The Genus Synchceta. By C. F. llousselct. 397 



Mr. Dixon-Nuttall's sketch very well represents its usual shape, 

 which of course varies slightly according as it is filled with food 

 or empty. The integument is thin, white, transparent, and shows 

 a number of fine longitudinal folds on the dorsal side. The 

 auricles are small, and in retraction are folded over the head by a 

 muscular band running from the auricle to near the centre of the 

 head. The front of the head is truncate and slightly rounded, 

 carrying the usual two pairs of styles, the outer pair arising from 

 well-marked triangular fleshy flaps. On the extreme raised front 

 of the head are two bundles of very fine diverging stiff setae, 

 similar to those found in S. ohlonga. The mouth is nearly central 

 in position, screened as usual by a row of fine, overhanging setse, 

 which can be seen from a dorsal view in this species. At some 

 little distance from and around the mouth are the usual four 

 bundles of three or four larger setae which are rather conspicuous. 

 The vibratile cilia are arranged on four ridges or cushions on the 

 front of the head, as is the case with all other species. The 

 cervical eye consists of a clear vesicle partly filled with white 

 opaque and red granules, the latter often separated into two 

 groups, and thus giving the appearance of a double eye. 



The mastax is large and of the usual Synchaeta type ; the jaws 

 are very delicate and difficult to make out ; they are of the same 

 type as those of S. trcmula, the unci are curved, and have four or 

 five teeth. 



The oesophagus arises on the dorsal side of the mastax and 

 leads into an ample stomach which is thick- walled anteriorly and 

 thin-walled posteriorly, and to which two elongated gastric glands 

 are attached. The ovary is large, flat, oval or nearly circular in 

 shape and contains large germ-cells. 



The lateral canals and contractile vesicles are of normal 

 structure. 



The dorsal antenna is situated on a raised prominence in the 

 usual position, and the lateral antennae are readily seen in the 

 lumbar region. The foot is stout and the two broad and pointed 

 toes are usually carried turned upwards. 



I have found the male of this species in March 1895 aud 

 several times since. It is a small, soft, conical animal with two 

 miuute toes, large sperm-sac, long brain with opaque granules at 

 the tip of which red granules forming a double eye are imbedded. 

 It is usually detected by its more rapid movements among the 

 females. 



Synchceta tavincc swims vigorously and steadily in spiral curves 

 and is rarely anchored to a thread, nor does it carry its eggs. Its 

 habitat is brackish water, and I have obtained it many times from 

 Mr. John Hood from the mouth of the Tay near Dundee, and also 

 from Great Yarmouth in water sent by Mr. H. E. Hurrell, generally 

 in the early spring, March and April. In size it reaches up to 



254 /* (to(7 ">•)• 



