443 PHYSIOLOGY OF THE INVERTEBRATA. 



amorOms sceva^ are apt to return, and she has been known to 

 sacrifice and devour her too long tarrying or dallying spouse. 



In the Arthrogastra the sexes are distinct. There are 

 three (?) ovaries consisting of many tubules united by trans- 

 verse anastomoses ; and two oviducts which unite in a short 

 vagina opening near the base of the abdomen. According 

 to Meckel, the oviducts dilate into a receptaculum seminis 

 before uniting with the vagina. The testes terminate in two 

 vasa deferentia, which unite before opening at the genital 

 aperture, the latter being situated at the base of the abdomen. 

 Just before the vasa deferentia unite, they receive two long 

 and two short caeca ; these organs have the function of 

 vesiculse seminales. There is a rudimentary penis, in the form 

 of a small papilla which projects out of the genital aperture.f 

 Unlike the Araneina, the palpi of the Arthrogastra take no 

 part in coition. The Arthrogastra are viviparous, the embryo 

 being developed in the ovaries ; and in Scorpio there is only 

 a partial segmentation of the vitellus, but in Ghelifer and 

 Obisium the segmentation is complete. In the Arthrogastra 

 there is no metamorphosis. :{: 



The Ckustacea. 



Among the Crustacea there are hermaphrodite as well as 

 dioecious animals. 



In the Ostraeoda, the ovaries are situated in " the valves 

 of the carapace, and terminate in oviducts, which open by 

 distinct apertures in front of the caudal appendage. Imme- 

 diately anterior to them are the openings of two horny 



* Sir Richard Owen's Comparative Anatomy and Physiology of the Inverte- 

 hrate Animals (2nd ed.), p. 462. 



t Like the genital organs of the Araneina, those of the Arthrogastra are 

 situated between the so-called "hepatic" lobes. 



+ Concerning the group of marine spiders (Pycnogonidea), see Den Norshe 

 Nordhavs-Maypedition [xx] by Dr. G. 0. Sars ; and Dr. T. H. Morgan's Em- 

 hryology and Phytogeny of the Pycnogonids (1891). These animals do not 

 belong to theArachnida or to the Crustacea ; but they, along with the Araoh- 

 nida and Crustacea, have come down the stream of evolution in parallel 

 lines. 



