OBSERVATIONS ON THE AQUARIA AT CENTRAL STATION. 
11 
would rernaiu ensconced in the shelter thus made, but no spawning was observed in. 
such situations, the preference appearing to be for the denser masses of plants high 
up or among the pebbles on the bottom. 
The spawning of the tessellated darter was wholly as described on the sheltered 
sides of stones, but their presence in the same tank may have interfered with the 
natural habits of the others. 
The quick, jerky, energetic, climbing and darting movements of both species are 
much like those of the nut-hatches among birds. 
BREEDING HABITS OF FRESII-WATER MUSSELS. 
Three species of Unionidw were under observation during the spring of 1890, which 
showed the manner of development and escape of the young. The accompanying 
sketches of two species are traced from water-color pictures by Mr. S'. F. Fenton. 
The specimens were not posi- 
tively identified by the concholo- 
gist who observed them. It will 
be seen that while the shells are out- 
wardly very much alike the peculiar 
development of the mantle is very 
different in each and would afford 
a ready means of identification in 
the breeding-season. 
The difference in color is also 
very great. In the one with the 
small tentacles the color of the 
mantle is white, tipped with pale 
yellow, with the gills, which also 
inclose the eggs and appear as the 
lobed central mass, a pale slate 
color. In the other the mantle is 
salmon color from pale to quite deep 
tints, while the egg-sack is purple. 
In each of them the peculiar 
processes or tentacles were kept 
constantly in motion, in the one 
waving like cilia, while in the other 
they were constantly clasped and 
unclasped, crossing as a pair of 
arms. 
No sketch was made of the 
third species. There was no such 
extensive development, there being simply two rows of short tentacles of equal length, 
which were kept in constant wave-like motion after the manner of cilia. 
The first two specimens were from ponds in which there is no current, and this 
probably accounts for the necessity of an extensive development of tentacles for the pur- 
pose of inducing circulation and providing food and fresh water. The third was taken 
