202 



SCIENCE-GOSSIP. 



on the ventral surface, followed by a tubular 

 pharynx, the walls of which are strengthened by a 

 cylindrical fascicle of corneous rods, or a simple 

 corneous tube ; no stylate appendages or fascicle 

 of caudal setae at the posterior extremity." 



Chilodon cucullus Miiller, is roughly oval in shape, 

 and is about twice as long as broad, the posterior 



Wmm 



Fig. 31. — Chilodon cucullus ( x 250). 

 gr, groove running to mouth ; p, pharj'nx, with rod basket- 

 work ; cv, contractile vacuoles; n, nucleus. 



end is rounded, and the anterior end bears on the 

 left side a lip-shaped prominence From the end 

 of this projection, a fine groove runs obliquely 

 inwards towards the oral aperture. A row of 

 adoral cilia runs along the front margin, and round 

 over the lip. The oral aperture is on the ventral 

 surface, and from it leads a tubular pharynx. 

 This is strengthened by rod-shaped pieces of 

 hardened cuticle, which form a framework to 

 it, something like the upright rods of a hamper. 

 They may be protruded slightly from the oral 

 aperture. The nucleus is oval or spindle-shaped, 

 and encloses a well-marked nucleolus ; numerous 

 contractile vacuoles are present, scattered over 

 the ventral surface of the body. The cilia are, 

 of course, confined to the ventral surface, and are 

 primitive in character. The length of the body 

 is from 100 to 300 microns. 



This species occurs very commonly in both salt 

 and fresh water. It presents a large number of 

 different forms, and thus has attained for itself 

 a long list of synonyms, which it is hardly worth 

 while to write down here. It is placed by Biit- 

 schli in the order Gymnostomata, which forms a 

 part of Stein's order, Holotricha. 



Family Oxytrychidae. — " Animalcules free-swim- 

 ming, ovate or elongate ; usually with a flattened 



or concave ventral, and a more or less convex 

 dorsal, surface ; peristome field ventral, triangular 

 or arcuate ; oral ciliary system consisting of an 

 outer or right-hand marginal fringe of powerful 

 adoral cilia, which is frequently supplemented by 

 oppositely reflected or left-hand marginal series of 

 smaller preoral cilia, and more rarely by a median 

 series of lax and alternate endoral cilia ; locomotive 

 cilia sitose, stylate or uncinate, variously distributed 

 upon the remaining ventral surface and forming 

 separate sets or groups, distinguishable as the 

 frontal, ventral, anal, marginal and caudal series ; 

 supplementary immobile, hispid, or hairlike setae 

 sometimes present on the lateral margin, or more 

 rarely on the dorsal aspect." 



Stylonichia mytilus Ehrenberg, is perhaps a 

 convenient type of the more highly developed 

 Hypotricha. The body is oval in shape, and 

 rather more than twice as long as broad, the front 

 end is rather wider than the hinder end, which 

 is often rather abruptly truncate. The cilia are 

 arranged as follows on the ventral surface. Five 

 groups may be distinguished, without considering 





Fig. 32. — Stylonichia mytilus ( x 250). 

 ft, frontal series of cilia; a, anal series of cilia; c, caudal 

 series of cilia; m m, marginal series of cilia; «, undulating 

 membrane. (The ventral series of cilia is not shown.) 



those bearing special relation to the peristome 

 field. The first group is called the frontal series, 

 and occupies the right-hand front portion of the 

 ventral side. The anterior : three or four in this 



