24 Transactions. — Zoology. 



Var. tenua. Figs, ix.c, \x.d. 



Varietal characters : Head small, and whole body slender. 

 Foot stout ; toes long. Distinct oblique furrow in the lorica, 

 running forwards and downwards from posterior edge. 



Colour, none except the deep-red cervical eye, and some- 

 times the brown cells round the stomach. In general shape 

 this variety is quite unlike the type, so different that I long 

 regarded them as distinct species. It is slender, and has not 

 the least sign of being bull-headed. The foot is stout, and 

 the toes very long. The toes are often spread out so that 

 they lie in one and the same straight line. The head is 

 slender, is not marked off from the body except by the edge 

 of the lorica, and has a downward flexure. The ciliary wreath 

 is much as in the type. The lorica encloses the body more 

 completely than in tauroceplialus itself. Its posterior edge is 

 distinct, and does not slope away forward, as it does in the 

 type. There is also a very distinct oblique furrow running 

 from the posterior dorsal edge downwards and forwards to 

 near the ventral anterior edge. The mastax is quite like that 

 of the former variety, but is a little stouter. The other parts of 

 the alimentary canal, the muscular bands, glands, excretory 

 and reproductive systems, do not call for remark. The eye 

 is small, but has behind it a small brain of a very light-pink 

 tint. 



This variety is on first appearance quite like D. pceta. The 

 general shape and the oblique lateral furrow lend themselves 

 to this impression. But the character of the eye is quite 

 different, and this variety is connected by such an unbroken 

 chain of slightly varying individuals with D. taurocephaliis 

 that there can be no doubt that the difference between them 

 is only varietal. I have described the two extremes of this 

 chain under the name of taurocej^halus and tenua, but all 

 intermediate stages are common. 



X. — Diaschiza semiaperta, Gosse. Plate X., figs. x. x.a. 



Specific characters : Body compressed, highest behind. 

 Lorica with the dorsal cleft closed in front, gaping behind, the 

 ventral edges apparently approximate. Eye frontal. Toes 

 long, slender, recurved. 



Colour, none except the small red eye. The shape is high, 

 narrow, and rather clumsy. The body has a hump-backed 

 appearance, the highest point being behind the middle of its 

 length. The body narrows abruptly into a short stump-like 

 one-jointed foot, ending in two extremely long and strong 

 toes, half as long as the body. The head, which is marked off 

 from the body only by its being not enclosed by the lorica, has 

 a downward flexure, and its anterior edge is quite oblique. 

 This oblique surface bears the cilia, and in its centre is a little 



