294 



nOTIFEHA. 



alimentary canal consists of oesophagus, mastax (chewing stomach), 

 glandular stomach, and intestine; all except the mastax cilated. 

 The mastax bears two chitinous jaws (trojohi), which in life are in 

 constant motion and comminute the food. The cerebral ganglion 

 lies above the oesophagus, with which simple eyes and peculiar sense 

 organs, the cervical tentacles, are frequently connected. The 

 usually single ovary and the paired protonephridia emjity into the 

 posterior part of the alimentary canal, which thus becomes cloacal 

 in character. For a long time males were unknown until Dal- 

 rymple discovered that these are much rarer and smaller ' dwarf 



Fig. 258.— Brac7iio)ms mrciilaris. A, female with four eggs in various stages; B. male ; 

 C, 'tlame' from protonephridia, greatly enlarged; /), urinary bladder; c, cloacal 

 opening; d, gastric glands; (/, ganglion, vrith eve; ft, testis; t, mastax; m, 

 stomach; o, ovary; p, penis; /, tentacle; ic, protonefihridia. 



males,' and that they have a much simpler structure (fig. 258, /.)• 

 Usually the alimentary tract is reduced to a solid cord in which the 

 testes are imbedded. 



The Rotifers have twt) kinds of eggs, large winter ega's enclosed 

 in a thick shell and smaller thin-shelled summer eggs. The latter 

 develop parthenogenetically and by their numbers aiul rapid 

 growth subserve the distribution i.if the species. The winter eses 

 require fertilization, and have a long resting period, thus serving 

 to tide over periods of cold or drought. The adult aninnils can 

 withstand a certain amount of desiccation; and they a.re often 

 found in damp moss or in cave troughs in a sort of sleep from 

 which they are awakened by water. 



