The Lake and Brook Lampreys of New York 447 



prej's are so vigorous and aggressive that, when hungry, the}- 

 will attack the ganoid fish, Amia calva, and rasp away the 

 scales sufficient!}' to extract blood from the amia. If they 

 naturally return to the lake and resume their ordinary mode 

 of life there should not be the slightest difficulty in deter- 

 mining it under the natural conditions just mentioned. It is 

 hoped that suitable facilities may be afforded at some future 

 time to settle definitely this important question and also sev- 

 eral others that have arisen in the study of the various stages in 

 the life history of these animals. 



DEVELOPMENT OF THE OVUM AND LARVAL LIFE. 



The ripe ova are about one millimeter in diameter and 

 nearly spherical. They are very opaque from the abundance 

 of opaque food yolk, and each is surrounded by a thin layer 

 of material which is very adhesive upon exposure to either air 

 or water, consequently the eggs adhere to whatever solid body 

 they come in contact. The adhesion is not very permanent, 

 however, as after a day or two they are easily detached. 



Some eggs of the brook lamprey were fertilized and kept 

 until the larvae were hatched. The segmentation is total and 

 unequal as in the amphibia, and the development proceeds 

 with great rapidity ; after eleven days the heart beats are 

 plainly visible. In 14 days the mouth is shark-like and on 

 the ventral side, and the blood vessels extend around the 

 gill slits. In 18 days the eyes are clearly shown, respiration 

 and the movements of the velum are evident and the mouth 

 has assumed the larval appearance with the hooded dorsal lip 

 so characteristic of the older larvae. The fins are represented 

 by a continuous fold from a point about opposite the 4th 

 branchiopore along the dorsimeson and around the tail on the 

 ventrimeson to the vent. In swimming the larva goes with a 

 wriggling motion ; it holds itself dorsal side up as do the older 

 larvae when swimming and like the older ones rests on the 

 side when quiet. 



As was shown by Calberla ('77), the nervous system de- 

 velops as a solid cord and becomes a hollow tube only later in 

 the course of development. In this respect the lamprey 



