332 C. T. ROUSSELET ON BRACHIONUS BAKERI. 



all correspond with or fit in between the forms illustrated in 

 the accompanying plate, and must be considered mere varieties 

 of this very variable species : — 



Brachionus bidentata, Anderson. 



„ rhenanus, Lauterborn. 



„ tuberculus, Turner. 



„ melhemiy Barrois and Daday. 



,, obesuSj „ 



„ granulatus, Kertesz. 



„ entziij France\ 



„ cluniorbicularis, Scorikow. 



I may add here that B. quadratus, which has been mentioned 

 as a link in the series of varieties of B. bakeri, does not belong 

 to this group. The whole type and character of the shell is 

 different ; it is very high and square behind, has no foot sheath, 

 and the structure of the shell shows a kind of closely reticulated 

 lacework, which is not found in any other species of BracJiionvs, 

 besides having a semi-jointed foot. 



The size of B. bakeri varies also greatly ; the largest speci- 

 mens, with longest spines, measure 73-in. (0339 mm.) from the 

 point of the anterior to the tip of the posterior spines, the more 

 ordinary forms are -g-^-in. to -g^in. long (0*282 mm. to 0*317 mm.), 

 whilst the very short spined varieties often do not exceed 

 Y^in. (0*254 mm.). 



Explanation of Plate XVI. 

 Fig. 1. Brachionus bakeri, type species, dorsal view. 



