FRESH-WATER FISHES OF NEW JERSEY. 99 
struggle for existence, and perhaps consider that the meta- 
morphoses 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 lavi Pack. la, 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. 
Tue character of the Delaware River, in the vicinity ot 
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 col- 
lections therefrom; but there is nothing i in the publications 
of their studies giving any knowledge of the habits of 
these fish, but siuply the fact of their presence in these 
waters. 
The ichthyic fauna is quad aay as some streams are cold 
and swift, that until lately harbored trout; and other 
streams, sluggish and thick, that are paradisiacal to the mud- 
fish (Melanura), and the sucker (Hylomyzon). 
