SCIENCE-GOSSIP. 



iog 



BRITISH INFUSORIA. 

 By E. H. J. Schuster, F.Z.S. 



{Continued from page 84.) 

 Part III. — Ciliata Holotricha. 



T^AMILY Trachelocercidae. — " Animalcules free- 

 swimming ; flask-shaped or elongate ; soft and 

 flexible ; ciliate throughout, the oral cilia slightly 

 exceeding in size those of the general surface ; the 

 anterior extremity often prolonged in a neck-like 

 manner, an annular groove or furrow often present 

 near the anterior extremity." 



Trachelocerca olor Muller. — When expanded it is 

 shaped like a soda-water bottle with a very long 

 neck. It is very contractile and moves its neck 

 about in every possible way, and in some positions 

 presents a swan-like appearance. The body is 

 strongly marked with spiral striations. There is 

 one contractile vacuole at the posterior end and 

 one or two near the anterior. The nucleus is 

 central in position and round or oval in shape ; 

 a small paranucleus is present, but is not easily 

 made out. The mouth is situated at the base of 

 a conical depression at the anterior end of the 

 neck and is surrounded by a circlet of cilia some- 

 what more prominent than those which cover the 



Fig. 24. — Trachelocerca olor ( x 200). 



general surface of the body. Biitschli compares it 

 to the cork in the mouth of a bottle. The length 

 of the body may be from 120 to 200 microns. The 

 species is common in pond water. 



Family Euchelyidae. — " Animalcules free-swim- 

 ming ; ciliate throughout, oral cilia slightly larger 

 than those of the general cuticular surface ; cuticle 

 soft and flexible ; oral aperture terminal or lateral ; 

 the anterior extremity of the body never prolonged 

 in a neck-like manner." 



Colpoda cucullus Ehrenberg. — This is kidney- 

 shaped ; the mouth, to which an oesophagus of 

 moderate size leads, is on the concave side of the 

 body. In the oesophagus there is a lip-like struc- 

 ture which stretches out beyond its opening to the 

 exterior ; this may be either an undulating mem- 

 brane or a tuft of more strongly developed cilia : 

 which, it is exceedingly hard to determine. In 

 the middle of the body an egg-shaped nucleus and 

 a small paranucleus may be seen, the former easily, 

 the latter with difficulty ; and at the posterior end 

 a simple contractile vacuole is situated. The 

 striation of the cuticle is oblique and very distinct. 



The process of transverse fission is more or less as 

 follows : the middle of the animal about to divide 

 becomes constricted and the oesophagus and mouth 

 disappear, the constriction deepens and a fresh 



Fig. 25. — Colpoda cucullus ( x 265). 



contractile vacuole is developed in the anterior 

 half ; the two halves gradually become completely 

 separated and a fresh mouth and oesophagus is 

 developed in each. Encystment in a spherical 

 cyst, with or without multiple fission, is a common 

 occurrence. The length of the body is from 50 to 

 100 microns. 



The species is exceedingly common, and often 

 occurs in vast numbers in pond water and vegetable 

 infusions which have been kept for some time. 



FamilyPleuronemidae. — "Animalcules free swim- 

 ming, more or less ovate ; ciliate throughout, oral 

 cilia diverse in character to those of the cuticular 

 surface ; oral aperture terminal or ventral, supple- 

 mented by an extensile and retractile hood-shaped 

 membrane or velum." 



Pleuronema chrysalis Ehrenberg. — This animalcule 

 is oval or lentil-shaped, with the ventral surface 



Fig. 26.— Pleuronema chrysalis ( x 335) 

 Animal at rest ; v, undulating membrane. 



flat, the dorsal surface convex, and with both ends 

 equally rounded ; down one side a narrow channel, 

 the " peristome groove," runs, and into this the 

 oesophagus leading to the mouth opens. From 

 one side of the channel along its whole, except the 



