512 K. I. MARKS AND W. WESCHE ON MALE ROTIFERS. 



when any species was becoming predominant by rapid partheno- 

 genetic multiplication, the appearance of the sexual period might 

 be looked for." * 



After considering the various theories, we are inclined to think 

 that the hypothesis advanced in the paper previously alluded to t 

 is still a reasonable explanation of the curious phenomenon of 

 the male of the Rotifera. Briefly recapitulated, it is this. The 

 male is gradually disappearing, and the stages of this process can 

 be seen in the various families and species, beginning with those 

 which possess a digestive apparatus, through those that are 

 highly organised, but have no digestive apparatus, to the 

 lowly organised Polyarthra and Fedalion, and ending with 

 the Bdelloida, in which sub-order no male has been seen, and 

 in which it is supposed they have ceased to exercise any function. 



As this interesting problem is still in an unsolved state, it is 

 highl}" desirable that the male should be studied in as many 

 species as possible, and its habits carefully noted. 



Explanation of Plate 26. 



Pig. 1. Brachionus quadratus, Rous,, J", dorsal view, fully ex- 

 tended. 



a. Lateral view. c. Spermatozoa. 



h. Dorsal view, retracted. d. Resting e^g. 



„ 2. Anurea brevispina, Gosse, c?, lateral view. 



a. Dorsal view. 



„ 3. Pterodina 2)citina,'Ei\\v., (^, lateral view. 



a. Dorsal view, retracted. h. Dorsal view, fully extended, 



* Biol. Centralhlatt 18, 1898, p. 173, 



f •' Observations on male Rotifers," W. Wesche, Journ. Quelt. Micro. 

 Cluh, Ser, 2, vol. 8, pp. 32G, 327. 



Jov-ra. Quekett Microscopical Club, Ser. 2, Vol. VIII., No. 53, November 1003. 



