BRACHIONUS QUADRATUS, AND BRACHIONUS RUBENS. 151 



B. leydigii has a square-shaped lorica like B. quadratics, 

 and a rounded median spine over the foot-opening like that 

 of the var. rotundas, while the lace-like structure of the lorica 

 and the papillose winter egg it has in common with both. 



However, the strongly tessellated dorsal surface of B. leydigii, 

 showing five rows of hexagons and pentagons, resembling in 

 prominence the facets of Anuraea serrulata, is a character which 

 is absent in the other two forms. Bilfinger mentions having 

 observed among his B. quadratus one specimen with faceted 

 lorica, resembling Cohn's figure ; and the fact of the identical 

 structure of the resting egg in all three forms is strong evidence 

 in favour of their being closely allied species. The resting eggs 

 in particular usually give the best characters to differentiate 

 closely allied species of Brachionus, as Oohn himself has mentioned 

 in his memoir of 18G2. 



It is quite possible, therefore, that these three forms may 

 eventually be found to be varieties of one species, in which 

 case B. leydigii would be the type species and the other two 

 varieties. However, before making such changes I should like 

 to have the opportunity of examining some faceted specimens 

 corresponding to Cohn's figure. My present object is merely 

 to record the rounded variety of this group of Brachionus. 



Brachionus rubens, Ehrenbenr 



.->• 



It is unfortunate that in Hudson and Gosse's monograph 

 B. rubens is wrongly figured, a fact which has caused considerable 

 confusion and difficulty in separating this species froinifr. urceolaris. 

 A glance at Ehrenberg's figures of B. rubens published in 1838 

 will show that the frontal teeth of the lorica have a peculiar 

 unsymmetric shape, each tooth showing a narrow anterior part, 

 and then slanting outwards and forming a broad base (best 

 understood by referring to Fig. 9), quite unlike those shown in 



