84 OENEEAL HISTOET OF 



This minute male being destitute of organs adapted to continue 

 its own existence, is developed solely for the purpose of impregnating 

 the lai'ger and more highly organized female animal, of which, 

 indeed, it is in part a parasite. 



The female reproductive organs consist of a single or double ovary, 

 an ovi-sac, oviduct, and vaginal orifice. The ovary, varies in size, 

 having tubes conducting from it to the cloacal outlet, through which 

 the ova escape. The ovary is situated at the hinder part of the 

 animal, along side the intestine. It is mostly seen to contain ova 

 in diiferent stages of development. The mature ova are invested by 

 a clear, but firm granular shell, mostly coloured, and containing a 

 colourless yolk, with a clear germinal spot. The development of the 

 embryo in the egg, proceeds as ia Invertebrata generally, the yoLk 

 Bubdividing by spontaneous fission, and, at length, evolving the em- 

 bryonic cell. The fully developed embryo is furnished with a 

 rotary organ, eye-spots, an oesophageal head, with its masticatory 

 apparatus, and, in fact, -with the entire characteristic organization of 

 the full grown animal. 



Mr. Gosse, in his paper on AsjjIancJma, says: "In no specimen 

 have I seen the ovary horned or band- shaped, but roundish and 

 very small." 



The ova, after impregnation, pass from the ovary into the ovisac, 

 and there go through various phases of development, like the 

 embryo of higher animals in the uterus. When sufficiently advanced, 

 the young being escapes into the oviduct, which conducts it through 

 the vaginal orifice into the cloaca, whence, after a variable time, it 

 IB expelled. 



During the residence of the embryo within the ovisac, it mostly 

 becomes enveloped in a sheU, of considerable strength and toughness, 

 which preserves it after extrusion from injury. To accommodate 

 the increasing size of the contained ovum, or ova, the ovisac is 

 capable of great distension, so much indeed, that it sometimes occu- 

 pies the larger portion of the interior of the animal. The cloacal 

 outlet, also, is very extensible, to allow the temporary retention and 

 subsequent passage of the very large matured eggs. In many Hota- 

 toria, the ova are not at once set free on their exclusion, but remain 

 adherent about the cloaca, as happens in many Entomostraca. 



