GENEEATIVE ORGANS OF ARTHEOPODA. 



295 



a CEecal uterus wliicli is continuous with the duct. At their hinder end 



they send off a short duct [od) to the generative pore. The organs 



of either side are united in the same way in the testis. This is 



formed of a double row of glandular follicles, which unite into a 



coiled canal, which forms the simple excretory duct and opens at the 



base of the last pair of feet. 



The generative organs of the Decapoda resemble those of Mysis, 



by being similarly connected in the middle line ; they appear to be 



further developed by various 



differentiations. The female ^ A 



organs are formed by two 



long tubes which run for- 

 wards and backwards, and 



are united transversely with 



one another; these tubes 



function partly as germinal 



glands, but chiefly as ovi- 

 duct and uterus. In the 



Crayfish the two anterior 



divisions have the form of 



short lobes, while the two 



hinder ones are fused into 



an unpaired piece. On each 



side a short duct passes to 



the genital pore, which in 



the Caridina has the same 



position as in the Schizo- 



poda; in the Macrura it is 



placed on the basal joints 

 of the third pair of feet, 

 but in the Brachyura on 

 the segment of the body, 

 which carries this pair. The Brachyura are also distinguished by a 

 pouch-like enlargement of the oviduct (seminal pouch). In the 

 male apparatus the testes are formed by two much-coiled tubes, 

 which are transversely connected with one another in front, and 

 which, like the female organs, lie for the most part in the cephalo- 

 thorax; in Pagurus only are they placed in the abdomen. In the 

 latter they give off two long and closely-coiled but gradually-widen- 

 ing ducts. Herein they agree with most of the Decapoda, but they 

 are distinguished from them partly by the increased size of the 

 lobes formed by the coils of the seminal canal, and partly also by 

 the formation of the unpaired piece, which unites the glands of 

 either side. The germinal glands are more completely united m 

 Astacus. A vas deferens with long coils passes on each side to the 

 outer generative orifice, which is placed, as a rule, on the_ basal jomt 

 of the last pair of feet; in the Brachyura, however, it is found at 

 the end of a penis, which is formed by a metamorphosed appen- 

 dage. The opening of the male apparatus only is then the same 



Fig. 155. 



Homarus. 



deferens. 



lyiale generative organs. A Of 

 BOfOniscus. ft Testes, vd Vas 



vs Seminal vesicle, o Its orifice. 

 ^ Copulatory organs. 



