342 MANUAL OF NATURAL HISTORY. 



2. Family. — Crab-Rotifers (Euchlanidse). Body lo~ 



ricated ; wheels many-parted. 



3. Family. — Rotifers-proper (Rotiferidse). Body 



without a shell ; rotatory organs two, se- 

 parate. 



4. Family. — Tortoise-Rotifers (Brachionidae). Body 



loricated; rotatory organ double. 



5. Family. — Tardigrade-Rotifers (Macrobiotidse). 



Body with four pairs of short legs, each end- 

 ing in two pairs of small claws. 



ASCIDIAN-POLYPS. 



The Ascidian-Polyps are compound plant-like ani- 

 mals of great interest and beauty ; on account of 

 their branching fronds and phytoid aspect they were 

 named by Ehrenberg Bryozoa, or "animal mosses;" 

 but the designation of our own countryman, J. V, 

 Thompson, claims priority. Although in general 

 they possess the form of the Polypifera, they have 

 been shewn to have an organization so superior to 

 that of the true Polyps as to authorize their removal 

 to another section. They are in fact provided with 

 a distinct alimentary canal with two orifices, and 

 externally are at once distinguished from the Poly- 

 pifera by the ciliated tentacles which surround the 

 , mouth. The individual polyp-like animals are fre- 

 quently lodged in little horny cells, which are some- 

 times isolated as in the genus Bowerhankia ; some- 

 times arranged side by side as in Eschara and Plus- 



