Tadpole snail. Physa gyrina, 

 showing the tapering foot, digi- 

 tate mantle margin, and long, 

 slender tentacles. 



Some of the smaller snails, Amnicola and Valvata, were wandering 

 about, the former crawling with a wabbly gait, rolling the shell from 

 side to side. In another part of the aquarium, a number of Pliysas 

 were crawling rapidly along the bottom. Some of these rose suddenly, 

 like the pond snails. Others descended from the top, suspended by 



a slender thread of mucus. Several of the 

 pond snails had crawled out of the water, and 

 were attached to the glass, a number of inches 

 from the surface. Several apple snails, as well 

 as other members of the water breathers, were 

 enjoying themselves by crawling about the bot- 

 tom, or on the sides of the aquarium, apparently 

 feeding ; their long tentacles were waving, and 

 their blunt, cylindrical rostrum was moving 



about like the nose of a hound on the scent. All of this animation 

 in the aquarium made it seem like a miniature world, as indeed it 

 really was. 



On the narrow end of the aquarium we discovered a number of little, 

 jelly-like masses, which Professor Parker told us were the eggs of the 

 Physa snail. They were nearly an inch in length and very narrow. 

 Each mass contained a large number of eggs. By the aid of a magnify- 

 ing glass we counted the eggs in three masses, and found one hundred 

 and thirty in one, one hundred and sixty in another, and two hundred 



in the third. The Professor placed one of these 

 masses under the microscope, and we observed 

 the little embryos slowly rotating about. 



" The egtrs of the fresh-water snails," said 



oo 



the Professor, " may be found any time during 

 April or May. The young hatch out in June. 

 They are transparent little animals, about one- 

 fiftieth of an inch in length. They are very 

 active, and eat voraciously of anything which 

 b they find. Some of the water-breathers lay 



Egg mass of Physa gyrina. a, 



egg-mass, showing position of but a single egg, which is inclosed m a round 



eggs in envelope; b. single egg, mi ,. , > > 



much enlarged, showing posi- capsule. 1 he young o the apple snails are 

 tion of rotating embryo. bom .^^ and .^ llliimte? transparent ani- 



mals, about one-eighth of an inch in length ; they are very active." 



Near the aquarium, the Professor had a snailery in which were 

 several dozen snails of various species. The snailery was made of an 

 aquarium about the size of the one in which the fresh-water snails 

 and clams lived; the bottom was covered with earth to a depth 



36 



