Ti 



The Genus Synchceta. By C. F. Rousselet. 27 



objects, as I have shown to be the case with some other rotifers, 

 such as Pedalion mirum* They never collide with others, how- 

 ever, in their incessant and quick movements through the water. 



The eggs of Synchaetae are clear and transparent, nearly 

 spherical, or slightly oval in shape, and contain usually a small 

 cluster of golden yellow granules. As a rule the eggs are laid in 

 the water, where they fall to the bottom, but having a sticky 

 surface they adhere to any plant or object which they may touch. 

 In a few pelagic marine species, i.e. S. baltica, cecilia, triophthalma y 

 and ncapolitana, the eggs are habitually carried about, attached to 

 the toes till hatched. In S. oblonga I have seen the extrusion of 

 an egg : it remained attached to the toes for a few seconds and 

 then fell off. S. stylata has developed an egg of very unusual 

 character, being surrounded by very fine, long, stiff spines, about 

 three times as long as the diameter of the egg, which prevents it 

 from sinking, and the egg consequently floats in the water, fig. 4a, 

 pi. IV. All these are summer eggs ; thick-shelled or spiny resting 

 eggs have not been observed in any species. Dr. Zacharias has 

 stated that in the lakes of the north of Germany S. pectinata and 

 tremula habitually carry their eggs attached to their toes, which 

 they certainly never do in this country, nor am I aware of anyone 

 else having observed this in any other part of the world. 



The males of Synchaetae are rather rare ; I have seen those of 

 the followiDg species : — & tremula, oblonga, tavina, cecilia, vorax, 

 ncapolitana, and littoralis, which are described in their places in the 

 following pages. Mr. John Hood has seen that of S. gyrina, and 

 has also reported to me doubtfully the male of S. pectinata. lii 

 every case the males are very small, conical in shape, with cervical 

 eye, four frontal styles, prominent dorsal and lateral antennae, and 

 devoid of mastax and intestine. It is strange, however, that no 

 fertilised resting egg has ever been observed in any Synchaeta, 

 though the males were occasionally present in great numbers. 



The Synchaetae, particularly pectinata and tremula, are not in- 

 frequently subject to both external and internal parasites. The 

 external parasites I have observed consist of Infusoria : a species 

 of minute vorticella with a very short stalk, which attaches itself 

 singly anywhere on the integument, and also Triclwdina pedieulus 

 the parasite of Hydra, which I have once seen running all over a 

 S. pectinata ; the connection, however, may have been quite acci- 

 dental and temporary. The internal parasites are more serious and 

 consist of numerous spherical bodies, 22 /* (j^ S q in.) in diameter, 

 filled with clear protoplasm and some fine refractive granules, and 

 of elongated sausage-shaped bladders 68 /.c (^4 ]n -) l° n £ D ) r 3 3 • 6 /* 

 ( -Ya 1 ^ in.) wide. At first these latter are similar in structure to 

 the spherical bodies, but afterwards the whole bladder becomes 



• On the Sense of "Visicn in Botifeis. Jomn. QueJ>ett Blicr. Club, vol. iv. 

 pp. 371-3 and 376-7 (1892). 



