OF THE ROTATORIA. 457 



ever, more conceivable that thej may pass from the cloaca into the respiratory 

 tubes, and escape into the general cavity through the \dbratile tags — supposing 

 these last to terminate by open mouths. On the other hand, it is just possi- 

 ble that some supposed examples of the presence of spermatozoa within the 

 abdominal cavity, have rather been instances of parasitic beings (Entozoa) in 

 the interior. Thus, in Hijdat'ina senta, Leydig describes the interior occupied 

 by many numerous active animalcules, which he refers to the genus Astasia. 



The minute male beings just considered are brought into existence for the 

 sole purpose of feitilizing the ova of the larger and highly- organized female 

 animals. In relation to the females, they may be looked upon as little other 

 than parasites ; they are even deficient in organs necessary- to cany on their 

 owTi existence : the one piu'pose of impregnating the opposite sex being 

 fulfilled, theii' career is ended ; and this career is so brief, that the complicated 

 apparatus otherwise required to nourish and sustain the beings can be dis- 

 pensed with. 



The early history of the male Eotifer is that of the female. The evolution 

 of the ovum from the ovary, and the changes transpiring in the contents of 

 the egg untn the several organs become distinguishable, are identical in the 

 two. The following particulars from Cohn's paper (Zeitschr. 1855, p. 471) 

 will serve for illustration. The males of Bracliionus iirceolaris are developed 

 from smaller eggs than the females, and which are adherent in large number 

 at the same time to the parent-animal. These eggs are very spherical, and 

 reach -g-J-jyth of an inch in length and ^-J^th in diameter. Their shell is more 

 delicate, the contents clearer and much more transparent, from containing 

 fewer granules, and of a pale-yellow hue, whilst the usual simimer eggs are 

 dusky grey. Even when matm-e, this greater transparency and absence of colour 

 persist. Fission proceeds in the same way as in the female ova ; and after 

 it has been many times repeated, the different organs of the embryo begin to 

 make theii' appearance, — the red eye-specks being among the fii^st. However, 

 unlike what happens in the female ova, no signs of the maxillary apparatus 

 come into view, but two or three dark heaps of granules which are not seen 

 in those. "When mature, the embryo springs from the shell through a trans- 

 verse rupture, and is then seen to have a totally different figure from the 

 female beings, and at least three times smaller. When completely extended, 

 it measm-es only between -g^rth and 2-^4^11 of an inch in length, and yi^th 

 to -gJ-oth in mdth, and is observed at the first glance to be destitute of" the 

 firm integument or shield of the female animals, and to have a short- cylin- 

 drical figure, prolonged anteriorly in the form of a short head separated by 

 a constriction from the body. The foot is short and tubular, the head crowned 

 by a flattened disk expanded into a wide margin, which is clothed with long 

 vibratile cilia and a few non-^ibratile bristles. Their movements are extra - 

 ordinaiily energetic. 



The same female may lay in succession several male ova. According to 

 Leydig, both male and female ova are not generated at the same time. The 

 small size and relatively incomplete organization of the male Rotifera is a 

 circumstance not peculiar to the class ; the like is seen in the imperfect 

 "imago" of many Insects, destined only to a sexual purpose, in the para- 

 site-like males of Lerncea, in the miniature and incomplete males of Daph- 

 niadce, and in the equally inferior male representatives of Polynoe, E:cogone, 

 and of the j^ematoda generally, among Vermes. Leydig, moreover, finds an 

 analogous fact in the Siphonophora, in which he assumes the so-called genital 

 capsules, distributed everywhere in the aggregate mass of animals, to have a 

 male character, and shows this opinion is in harmony with the views put 

 forward by Leuckart respecting them. 



