23° AQUATIC MICROSCOPY FOR BEGINNERS. 



light. Each Rotifer inhabits a gelatinous tube of its 

 own secretion, but these sheaths are so closely pressed 

 together that they soon become confluent, or coher- 

 ent, and the jelly-mass seems to be common property. 

 This is especially true with the older and larger colo- 

 nies, which are formed by the pretty constant addition 

 to them of young Conochili, the whole cluster thus 

 varying in age with the age of its members, and 

 gradually but surely increasing in size, until the mass 

 becomes so large that it breaks apart, the separated 

 groups sailing off as if nothing unusual had occurred. 

 These Rotifers have their feet directed toward a 

 common center, the bodies radiating outward, and the 

 ciliary disk of each projecting, with a portion of the 

 body beyond the mucus and into the water. The ciliary 

 disk is horseshoe-shaped. As many as a hundred 

 members have been seen in a' single colony. Repro- 

 duction is by means of eggs. 



g. Philodina (Fig. 162). 



This particular species is readily distinguishable 

 from the common Rotifer (Rotifer vulgdris) by the 

 spines scattered over the back and sides of the hardened 

 and minutely roughened body, and by the 

 fact that the two eyes are placed, not on 

 the prf)boscis, but at some distance behind 

 the froiit border, while in Rotifer vulgdris 

 they are close together on the proboscis. 

 This position of the eyes, or what is called 

 the cervical position, is an infallible point 

 by which all members of this genus may be 

 Fig. i62.-Phii- distinguished from all the members of the 



odlna acu- 



leata. genus Rotifcr. 



