The Genus Synchceta. By C. F. Rousselet. 277* 



up to 408 n (^ in.) long by 231 p, (y^ in.) wide at the auricles. 

 Egg spherical, 98 ■ 5 /* (%%-g in.) in diameter. Lacustrine. 



This handsome rotifer, one of the most common and widely 

 distributed species in England, as well as on the Continents of 

 Europe and America, appears to have first been recorded by 

 Ehrenberg in 1831, in a communication to the Berlin Academy 

 of Science, and afterwards in 1838 in his great work on the In- 

 fusoria. 



In 1870, Dr. C. T. Hudson subjected this species, under the 

 name of S. mordax, to a careful study, which was published in 

 the Monthly Microscopical Journal, vol. iv. pp. 26-32, with a 

 plate of good figures, showing its various aspects. The animal 

 Mr. Gosse has figured as S. oblonga in The Botifera is certainly 

 a S. pectinata, swollen and half dead ; the two frontal processes 

 are sufficient to identify it as such. 



Synchosta pectinata is a well characterised species, which cannot 

 be mistaken when once seen. Its large sized, white, very trans- 

 parent, more or less conical body, and large prominent auricles, 

 make it a conspicuous object even with the naked eye. But its 

 special character, which serves best to distinguish it at once from 

 its congeners, are two fleshy setose protuberances, or little horns, 

 on the front of the head ; no other species of Synchseta has these 

 organs. 



The shape of the body is that of a more or less swollen cone, 

 very broad and convex anteriorly, ending in a short stout foot and 

 two minute conical toes. The exact shape of the body varies a 

 good deal. Young animals have straighter sides than represented 

 in fig. 1, whilst occasionally extra well fed specimens are met with 

 which are more swollen round about the stomach. 



The head is very broad, and, with the auricles, forms a wide 

 semicircle ; dorso-ventrally it is a little compressed, rising only to a 

 prominence on the dorsal side where the dorsal antenna protrudes. 

 The ciliary wreath consists of two parts : the dorsal part is 

 formed by a nearly straight double cushion of vibratile cilia, 

 interrupted in the centre ; the ventral part forms a smaller rounded 

 double cushion of cilia below and at the sides of the mouth, and 

 these cilia are mainly concerned in driving food-particles to the 

 mouth. The prominent auricles are large, semicircular, slightly 

 pendent, and furnished with long, powerful vibratile cilia, all 

 iirising on the upper surface of the auricles, from a cushion of 

 dense grey protoplasmic material. The auricles are supplied with 

 a number of muscular bands, arising from the integument of the 

 head and body-cavity, which can retract and also alter the position 

 of these organs, and thereby vary the incidence of the beat of the 

 cilia. This explains the vigorous turning movement and gyrations 

 which the animal performs with such rapidity. 



