ANTARCTIC ROTIFER A 51 



None of them, except A. grandis, is very common. That species swarms in numbers 

 - only inferior to those of Philodina gregaria. 



Adineta grandis, sp. n. (Plate XIL, Figs. Wa-Wd) 



Specific characters. Very large, stout, rostrum philodinoid, with lamellae and 

 brush of cilia as in Philodina ; posterior margin "of mouth pectinate : spurs short 

 broad cones, separated by straight interspace, reproduction viviparous. 



Detailed description. Large examples measure 750 M in length. The colour is 

 light brown or yellowish, darker in the alimentary tract. It has the graceful form 

 usual in the genus, very broad in the central region of the trunk and tapering to 

 narrow extremities. The trunk is regularly, and not very deeply, plicate. The 

 neck is slightly constricted below the head, then there is an expansion at the normal 

 level of the mastax. 



The head is ovate, and rounded in front. The rostrum is short and stout, 

 and is quite like that of a typical philodine, except that it is not retractile. 

 In ventral view the lamella?, which are relatively smaller than is usual in the genus, 

 appear to meet in the middle line. Beneath them is the brush of cilia, looking as 

 they do in a philodine when contracted, but the tip was never seen everted so as to 

 make the brush project. On each side, close to the edge of the lamellae, is a longer 

 cilium, moving like the tactile setae occurring in the same situation in Philodina 

 macrostyla, &c. Only one could be distinguished at each side. The antenna is 

 short and broad. 



The pectinate part of the mouth appears to be a' fold within the margin proper- 

 The processes are flat plates, with the spaces between about equal to the thickness of 

 the plates. They are rounded at the ends. The number varies from six to ten on 

 each side. At the inner end of each series the terminal process is drawn out into a 

 longer narrow rod, which appears to be attached to the flat surface of the corona. 

 The furred surface is uninterrupted from side to side, but at the anterior end a tooth- 

 like process projects backwards in the median line. The jaws are normal, with the 

 usual two teeth on each. 



The stomach is large and of a warm brown colour. The intestine is elliptical. 

 The two segments can be distinguished in the rump, which tapers gradually in line 

 with the stout four-jointed foot. The spurs are stout and subacute. They diverge 

 widely and are separated by an interspace about equal to the diameter of the spur at 

 its base. The terminal joint of the foot is of moderate length and the three toes are 

 small and short. 



The stoutness of the trunk varies greatly according to the number of young 

 carried, and their degree of development." It becomes enormous when it contains 

 six or seven young almost full-grown. The largest number observed was seven, but 

 the usual number was three. It was noticed that when the young were well enough 



