12 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
from a rapid stream flowing into the Potomac and, having abundance of circulation 
through natural currents, did not need so elaborate a development of tentacles. 
The authorities say of the generative habit that the eggs are fertilized in the fall of 
the year and are carried by the female through the winter, meanwhile undergoing devel- 
opment to the swimming stage. About March they make their escape and enter into the 
swimming stage, during which they are armed with hooks, by means of which they fasten 
themselves to aquatic animals, where they undergo further development, finally dropping- 
off and sinking to the bottom as the fully developed mussel, but still very minute. 
A PECULIAR HABIT OF A IIOLOTHURIAN. 
A holothurian, or so-called sea-cucumber, in one of the tanks was observed to 
eviscerate itself, as is their known habit. It immediately put forth a new set of bran- 
chiae, very delicate and transparent, but somewhat smaller than usual. This would 
indicate that the new organs are developed before the old are thrown away. The 
branchiae of this species of holothurian are ordinarily dark gray in color. The new 
ones were white, translucent, and beautifully lobed and branched, not having the usual 
fringed appearance given to them by the development of numbers of still more minute 
lobes. They were evidently only partly developed and looked like some of the small 
and delicate red algae with all the coloring matter bleached out. 
SPAWNING OF OVO-VIVIPAROUS FISH. 
The top-minnows (Gambusia patruelis) have frequently brought forth their young- 
in an aquarium and they have been reared to maturity, but all attempts to observe 
the method of fertilization or the extrusion of the young have failed. 
In conclusion it may be said that many minor observations of more or less value 
to science or practical fish-culture have been made. 
Altogether the results herein noted, while not extremely important, point to possi- 
bilities of great practical value when adequate facilities are afforded. 
