46 H. G. Kribs 



with sensory hairs lying on the inner side of the epidermis (Brace 

 'oi). At its base the lateral edges of the prostomium fold into 

 the buccal cavity. The ridge thus formed about the mouth pos- 

 sesses larger cilia than those present on other parts of the prosto- 

 mium and the beat is correspondingly slower. Surrounding 

 the mouth from the rear and running forward and upward, so as 

 to partially overlap the rear lateral edges of the prostomium, is a 

 a prominent under lip or peristomium. This lip may be so ex- 

 tended that it practically reaches the size of the prostomium, or 

 so far withdrawn that it becomes almost invisible. It is notciliated 

 The pharynx is a pear shaped organ and very muscular. It is 

 attached to the body wall, caudad, by a series of muscle fibers. 

 The anal segment has two papillae at its tip, similar in shape 

 and function to the toes of a rotifer. These papillae seem to have 

 been overlooked in previous observations on the structure of 

 iEolosoma. 



There are two layers of muscle fibers, one circular and one 

 longitudinal, lying close to the inner side of the epidermis through- 

 out the body segments. These muscle fibers are capable of enor- 

 mous contraction and extension. Within the epidermis are 

 numerous gland cells, some of which secrete mucus, while others 

 secrete an oily substance which is scattered in characteristic 

 "globules" throughout the epidermis. There is a thin semitrans- 

 parent membrane forming the outer layer of the epidermis, and 

 but loosely connected with the other epidermal aggregates. 



.^olosoma is hermaphroditic. It also reproduces by the for- 

 mation of zooids in a way similar to that of Stenostoma. I have 

 never found anv specimens that were sexually mature. They 

 have been observed, however, by D'Udekem ('62), Maggi ('65), 

 Stole ('89), and Nelson ('06). 



Move??ients and Reactions in a State of Mature 



The food of T^iolosoma consists largely of bacteria, diatoms, 

 unicellular algae, and the soft mesophyll tissues of decaying leaves. 

 When feeding the pharynx is generally progruded so as to come 

 in contact with the substratum. The peristomium is also con- 



