DESICCATION IN PHILODINA ROSEOLA. 363 



x 



This sphincter has been described by other authors but sections 

 of it in Philodina have never been shown. 



It is evident then, that the contractile bladder is not an 

 independent structure connected to the posterior part of the 

 gut by a narrow neck but is only a portion of the wall of the 

 gut modified to permit its distension. Its periodic contractions 

 force the collected liquid waste to the exterior without further 

 contractions of other parts of the cloaca. The more solid waste 

 from the digestive canal is forced out of the "blasendarm" by 

 independent contractions of the latter structure. 



B. The Contracted Animal. The closely packed condition of 

 the organs in the folded animal is shown in Fig. 13, Plate IV. 

 The cilia of the trochal discs and some of those lining the pharynx 

 will be noticed. On either side of the infolded trochal cilia are 

 the ends of the large glands connected with the mastax and 

 with the anterior end of the stomach-intestine. The edge of 

 the chewing apparatus is shown in the middle of the section, 

 while surrounding it will be seen the stomach tissue and a small 

 part of its lumen. The folding of the integument of the animal 

 is well shown here, especially at the anterior end where the 

 convergence of the longitudinal folds shows in section as a rosette. 

 It is apparent that in the contracted condition most of the water 

 which circulates in the body spaces is lost, for the organs lie 

 close to each other in contrast to the condition shown in Figs. 

 i, 2 and 3 where the spaces, especially those between the integu- 

 ment and internal organs, are very large. Fig. 14, Plate IV., 

 shows a section through a slightly different plane in an undried, 

 contracted animal. In the central part of the section the cells 

 of the outer part of the brain are shown while around the peri- 

 phery various gland cells appear. This section also goes through 

 one of the vitellaria and shows its characteristic form and struc- 

 ture. 



C. The Dried Animal. In the desiccated animal the arrange- 

 ment of organs is in no w r ay different from that in the previously 

 described contracted, normal ones. The organs are still more 

 closely apposed and the folding of the integument is closer and 

 better marked. 



Fig. 1 6, Plate IV., shows a section of a rotifer which was dried 



