WITH DESCRIPTION OF A NEW BRACHIONUS. 63 



the uterus of a saccate female. The change takes place more 

 or less suddenly from one generation to the next. The general 

 anatomy of A. Silvestrii follows that of other allied species, 

 and but few points need be mentioned. The two gastric glands 

 are large and kidney shaped, and are attached to the long and 

 rather wide oesophagus. The stomach has the usual structure 

 of large, dark-coloured granulated cells. The ovary has the 

 form of a narrow horseshoe-shaped band with a single row of 

 germ cells. An enlarged view of one of the lateral canals 

 with the contractile vesicle is given in fig. 8. The flame cells 

 are closely set and numerous, numbering over thirty ; the fine 

 tube to which they are attached adheres for some distance 

 to the nerve-thread of the ventro-lateral antenna on each 

 side. 



The sense organs consist of three pairs of antennae, namely 

 two on the front of the head, two dorso-lateral and two 

 ventro-lateral in position, each ending in a rocket-shaped organ 

 with a tuft of stiff hairs on the outside. Two finger-like, 

 fleshy processes are seen, one on each side of the head close 

 to the corona. Daday mentions that the animal has three red 

 eyes, but I could discover only a single small cervical red eye, 

 situated on the small brain. 



The male (figs. 5 and 6) is of usual structure, and has two 

 lateral humps, like the male of A. amphora. 



Greatest size of female 1,150 /x (l/22nd inch) in length ; male 

 408 jx (l/64th inch) ; jaws 164 fx (l/155th inch) ; resting-egg 

 195 /x (1/1 20th inch) in diameter. 



I am greatly indebted to Mr. Hammond for the excellent 

 figures of A. Silvestrii on Plate 5. 



It is quite possible that farther plankton collections, and 

 particularly collections made amongst the aquatic vegetation 

 near the shores and in the bays of Devils Lake, may reveal 

 additional species of Rotifera, but a great crowd of freshwater 

 forms cannot be expected to inhabit this brackish and alkaline 

 lake. 



