86 TBANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



lips measures only one-fourth of the width of the body at the 

 commencement of the intestine. Posteriorly the body 

 tapers only slightly to the anus, and in the male even in a 

 less degree than in the female. 



The cuticula is moderately thick, measuring 2 — 3 p in 

 the middle of the body, and is formed by several layers. 

 Externally, three very thin layers are found, which are 

 followed by a thicker one, and the latter finally is still 

 separated internally from the muscular layer by one or 

 two that are also very thin. The cuticula is smooth, not 

 annulated, at least the outermost layers, but the internal 

 thin layers are, perhaps, very finely striated. The 

 described thick middle layer of the cuticula is still con- 

 siderably more thickened on the tail ; in the male it 

 produces the bursa, and in the female the singular form 

 of the tail is occasioned by it. When these worms, while 

 swimming, bend and curve their bodies, transverse plaits 

 are formed by the outermost layers of the cuticula, similar 

 to those that were described by Glaus for Bhabd. brevi- 

 spincu. In the male a very narrow lateral membrane was 

 observed, only 5 /* broad in the middle of the body, i.e., 

 one-twelfth of the body-diameter ; in the female I did not . 

 observe it positively, but I think the female will also 

 prove to be provided with it. The rather broad lateral 

 fields measure one-third of the body- diameter. 



The head of our species (PL V, fig. 3 a) is surmounted 

 by six lips, that are separated from one another by rather 

 shallow notches. The lips are only 3"6 ^ high, this height 

 being about equal to one-fourth the diameter of the head at 

 the base of the lips ; the latter are accordingly low, and each 

 is surmounted by an extremely small papilla, that becomes 

 only conspicuous when highly magnified (Seibert, Immer- 

 sions-system, No. VIII). The lips are separated by a 

 hardly perceptible constriction from the contiguous part 



