i GENERATIVE ORGANS AND DEVELOPMENT 19 



opening. The ovaries always contain spermatozoa, some of which 

 project through the ovarian wall into the body cavity. Sperma- 

 tozoa are not found in the uterus and oviducts, and it appears 

 probable that they reach the ovary directly by boring through 

 the skin and traversing the body cavity. 1 In the neotropical 

 species there is a globular receptaculum seminis opening by two 

 short ducts close together into the oviduct, and there is a small 

 receptaculum ovorum with extremely thin walls opening into the 

 oviduct by a short duct just in front of the receptaculum seminis. 

 The epithelium of the latter structure is clothed with actively 

 moving cilia. In the Xew Zealand species there is a receptaculum 

 seminis with two ducts, but the receptacula ovorum has not 

 been seen. 



There appear to be present in most, if not all, the legs some 

 accessory glandular structures opening just externally to the 

 nephridia. They are called the crural glands. 



DEVELOPMENT. 



As stated at the outset, Peripatus is found in three of the 

 great regions, viz. in Africa, in Australasia, and in South America 

 and the West Indies. It is a curious and remarkable fact that 

 although the species found in these various localities are really 

 closely similar, the principal differences relating to the structure 

 of the female generative organs and to the number of the legs, 

 they do differ in the most striking manner in the structure of 

 the ovum and in the early development. In all the Austral- 

 asian species the egg is large and heavily charged with food- 

 yolk, and is surrounded by a tough membrane. In the Cape 

 species the eggs are smaller, though still of considerable size ; the 

 yolk is much less developed, and the egg membrane is thinner 

 . though dense. In the neotropical species the egg is minute 

 and almost entirely devoid of yolk. The unsegmented uterine 

 ovum of P. Novae- Zealandiae measures 1'5 mm. in length by '8 mm. 

 in breadth ; that of P. capensis is '56 mm. in length; and that 

 of P. Trinidadensis '04 mm. in diameter. In correspondence 

 with these differences in the ovum there are differences in the 

 early development, though the later stages are closely similar. 

 But unfortunately the development has only been fully worked 

 1 See Whitman, Journal of Morphology, vol. i. 



