what pointed. The third segment of the thorax is as wide as the head, and the legs are thick, the femora being broad. It is allied to C. piceum Denny, which in Europe lives on the Sandwich Tern.

The most degraded genus is Gyropus, of which Mr. C. Cook has found G. ovalis of Europe abundant on the Guinea pig. A species is also found on the porpoise; an interesting fact, as this is the only insect we know of that lives parasitically on any marine animal.

Fig. 29.

α

The genus Goniodes is of great interest from a morphological and developmental point of view, as the antennæ are described and figured by Denny as being "in the males cheliform (Fig. 29, a, male; b, female); the first joint being very large and thick, the third considerably smaller, recurved towards the first, and forming a claw, the fourth and fifth very small, arising from the back of the third." He farther remarks, "the males of this [G. stylifer, which lives on the Turkey] and all the other species of Goniodes, use the first and third joints of the antennæ with great facility, acting the part of a finger and thumb" (Denny's Monographia Anoplu- Antennæ of Goniodes. rorum Britanniæ, 1842, p. 155 and 157). The antennæ of the females are of the ordinary form. This hand-like structure, is so far as we know, without a parallel among insects, the antennæ of the Hemiptera being uniformly filiform,* and from two to nine-jointed. The design of this structure is probably to enable the male to grasp its consort and also perhaps to cling to the feathers and hairs, and thus give it a superiority over the weaker sex in its advances during courtship. Why is this advantage possessed by the males of this genus alone? The world of insects, and of animals generally abounds in such instances, though existing in other organs,

Except in Ranatra and Belostoma where they are disposed to be flabellate, i.. rudely pectinated on one side.

and the developmentist dimly perceives in such departures from a normal type of structure, the origin of new generic forms, whether due at first to a "sport" or accidental variation, or, as in this instance perhaps, to long use as prehensile organs through successive generations of lice having the antennæ slightly diverging from the typical condition, until the present form has been developed. Another generation of naturalists will perhaps unanimously agree that the Creator has thus worked through secondary laws which many of the naturalists of the present day are endeavoring, in a truly scientific and honest spirit of inquiry, to discover.

In their claw or leg-like form these male antennæ also repeat in the head, the general form of the legs, whose prehensile and grasping functions they assume. We have seen above that the appendages of the head and thorax are alike in the embryo, and the present case is an interesting example of the unity of type of the jointed appendages of insects, and articulates generally.

Another point of interest in these degraded insects is, that the process of degradation begins either late in the life of the embryo or during the changes from the larval to the adult, or winged state. An instance of the latter may be observed in the wingless female of the canker worm, so different from the winged volant male; this difference is created after the larval stage, for the caterpillars of both sexes are the same, so far as we know. So with numerous other examples among the moths. In the louse, the embryo, late in its life, resembles the embryos of other insects, even Corixa, a member of a not remotely allied family. But just before hatching the insect assumes its degraded louse physiognomy. The developmentist would say that this process of degradation points to causes acting upon the insect just before or immediately after birth, inducing the retrogression and retardation of development, and would consider it as an argument for the evolution of specific forms by causes acting on the animal while battling with its fellows in the

struggle for existence, and perhaps consider that the metamorphoses of the animal within the egg are due to a reflex action of the modes of life of the ancestors of the animal on the embryos of its descendants.

EXPLANATION OF PLATE 1.

Fig. 1. Colpocephalum lari Pack. 1a, antenna. The short line by the side gives the length of the insect.

Fig. 2. Lipeurus corvi Pack. 2a, antenna.

"3. Docophorus buteonis Pack. 3a, antenna.

"4. Lipeurus elongatus Pack. 4a, antenna.

"5. Nirmus thoracicus Pack.

"6. Lipeurus gracilis Pack.
"7. Docophorus hamatus Pack.

NOTES ON FRESH-WATER FISHES OF NEW JERSEY.

BY CHARLES C. ABBOTT, M. D.

THE character of the Delaware River, in the vicinity of Trenton, New Jersey, the head of navigation, is quite varied; the bed is stony, with scattered large rocks above the rapids, and sandy, with some vegetation below the falls; the current is swift to the rapids, but less so, being tide water, below them; these conditions, with that of the varied character of the tributaries at and near Trenton, make it an excellent point at which to examine the ichthyology of this river basin. This has been done partly by those who have received collections therefrom; but there is nothing in the publications of their studies giving any knowledge of the habits of these fish, but simply the fact of their presence in these

waters.

The ichthyic fauna is quite large, as some streams are cold and swift, that until lately harbored trout; and other streams, sluggish and thick, that are paradisiacal to the mudfish (Melanura), and the sucker (Hylomyzon).