BRACHIONUS QUADRATUS, AND BRACHIONUS RUBENS. 149 



very different appearance from the type. As, however, inter- 

 mediate forms occur, it seems unnecessary to make even a variety 

 of these extreme forms. 



The internal anatomy is quite normal, and follows that of 

 B. urceolaris. The foot is long and wrinkled, except a short 

 distal piece, which carries the two small conical toes. 



The usual three kinds of eggs have heen observed ; the small 

 male eggs and larger female eggs have the usual structure ; the 

 fertilised resting egg is broader at one end and has a thick shell 

 which is deeply pitted, and the rounded contents inside only fills 

 about half the cavity of the eggshell. 



The male was obtained by isolating and hatching some male 

 eggs ; it has the usual characters of the Brachionus males, and 

 its integument is but slightly chitinised ; Fig. 4, PI. 11, drawn 

 by Mr. Dixon-Nuttall from a preserved specimen, gives a good 

 idea of its appearance. 



Size of lorica : female, length 292 /x (^ T in.), width 231 jx 

 ( t !tj- in.) ; size of male, 120//. (o TT j- in.) : of resting egg 136 /t 

 (tJs in -); female egg 110 /x ( 2 ^ in.). 



Brachionus quadratus var. rotundus, n. var. 



Since the discovery of B. quadratus in 1889, I have found this 

 species in many localities around London, and often in consider- 

 able numbers in the Regent's Canal. It has also been sent to 

 me from various parts of England, so that it is evidently a widely 

 distributed species. Bilfinger has recorded it from Wiirttemberg, 

 and in 1905 I collected it in the Koorn Spruit, Orange River 

 Colony, in South Africa. 



Some two years ago Mr. John Wood sent me from Dundee a 

 Brachionus which he could not name, but which I soon recog- 

 nised by the peculiar lace-like structure of the lorica as a 

 remarkable variety of B. quadratus, in which the sharp postero- 

 lateral corners of the type species have become rounded off, as 



