10 THE ROTIFERA. 



The Reproductive System. 



The reproductive system of the female is only too conspicuous ; as the presence of a 

 large ovary (figs. 1, 2, oy), and of one or two opaque ova in different stages of growth, 

 frequently obscures the sight of the other organs. 



The ovary is studded with large and rather irregularly shaped germs (figs. 1,2,0); and 

 the ova (fig. 1, om), so long as they are within the body, are dark, granular, and homo- 

 geneous. The ovary opens doubtless by an oviduct into the cloaca, but this I have not been 

 able to see. This is the arrangement that exists in other cases wherever I have seen 

 the oviduct. The mature ovum is expelled very quickly ; and the egg often remains 

 attached to the animal by a thread till the young escapes by rupturing the shell (if it 

 may be so termed) in which it is inclosed. If, however, a Brachiomis, with two or 

 three eggs attached, be held in the compressorium, it will frequently free itself by 

 pushing with its foot against the eggs, and so breaking the threads. 



The Egg. 



Of the eggs and their development it is unnecessary here to say more than that 

 B. rubens has two kinds of female eggs, nearly of the same size ; of which the one has a 

 smooth, transparent, membranous covering or shell, while the other has a thick opaque 

 shell, ornamented with hemispherical knobs. The former is the ordinary " summer " 

 egg, and the latter the so-called " lasting," " winter," or " ephippial " l egg. In shape, 

 too, the ephippial egg differs from the ordinary female one. It is much bigger at one end 

 than the other, and at the smaller end there is a projecting neck and cover (fig. 16). 



The male eggs are smooth and semi-transparent like the ordinary female egg ; but 

 are somewhat rounder in shape, and barely half the size. They occur, too, in larger 

 clusters ; for while it is iisual to see only two or three smooth female eggs, or one 

 ephippial egg, attached to the mother, no fewer than eight or ten male eggs may be seen 

 carried about together. 



The Male. 



The young female Brachionus when hatched resembles its mother ; but the young 

 male is a widely different animal (figs. 13, 14). It is about one-third of the length of 

 the adult female's lorica, and it has neither lorica, mastax, jaws, nor stomach. 



The head bears a simple circle of long cilia, and there is a red eye on a cephalic gan- 

 glion placed just as it is in the female. The vascular system, with its tortuous 

 canals, vibratile tags, and contractile vesicle, is also present ; and the foot is furnished 

 with the usual pair of glands ; but of a nutritive system there is not the slightest 

 vestige. 



Nearly half the body is occupied by a great sperm-sack (figs. 13, 14, ss), in which 

 under favourable circumstances the spermatozoa themselves may be seen in motion. 

 The sperm-sack ends in a short protrusile tube, ihepenis (figs. 13, 14, _p), ciliated at the 

 end, and placed just above the foot. 



In the larger and more transparent males of other genera notably in that of 

 Asplanchna Ebbesbornii there are special muscles for drawing back the protruded 

 penis ; and, though I have failed to see these in the male of B. rubens, it probably 

 possesses a similar structure. 



This strangely unfurnished creature leads a brief life of restless energy, now darting 

 from place to place, so swiftly that the eye can scarcely follow it, and now whirling 

 round as if anchored by its curved foot and penis. 



It often circles round the female, attaching itself now here, now there, and forcing its 

 companion to waltz round and round with it, from the top of the phial to the bottom. 

 With animals so active and so small it is difficult to be certain of having seen actual 



1 So named by Prof. Huxley from the resemblance to the lasting-eggs of the Daphniro. These 

 latter were called " ephippial" by Mailer from their shape, which is that of an ephippium, or saddle. 



