206 Description of the Plates. 



g. Anus, opening on ttie inferior surface of the ' telson' in uncal- 

 cified membrane, just anteriorly to the line of junction of 

 its anterior and posterior halves. 



h. Heart, showing one of the lateral venous orifices, and its 

 posteriorly placed bulbus arteriosus dividing into two main 

 branches, the larger one of which passes vertically down- 

 wards at j, and is known as the sternal artery ; whilst the 

 other passes along the dorsal surface of the intestine at ^, 

 and may be called the post-abdominal artery, and taken to 

 represent the posterior chambers of the elongated vasiform 

 heart seen in many lower Crustacea. 



i. Post-abdominal artery, taking a course superiorly to the intes- 

 tine, and inferiorly to the extensor muscles of the posterior 

 segments. 



j. Sternal artery passing down towards the orifice in the com- 

 missural cord connecting the third and the fourth abdominal 

 ganglia. 



k. Hepatic artery of the left side, passing down from the heart 

 on to the pylorus towards the hepatic lobes of that side 

 which have been removed. 



I. Anterior left lobe of testis. 



V . Azygos lobe of testis placed posteriorly to the paired lobes 

 of the two sides with which it is continuous. 



m. Convolutions of vas deferens of left side, in length equal to 

 that of the entire body. They probably secrete the agglu- 

 tinating matter of the spermatophores. %ere are in most, 

 if not all, Crustacea and Myriapoda, and in the higher 

 Arachnida, two separate outlets for the vasa deferentia, one 

 on either side of the body, howsoever much intercommuni- 

 cation of the glands or ducts may take place distally to the 

 outlets. The Insecta, on the other hand, have ordinarily a 

 single ductus ejaculatorius, as also a single vagina, into 

 which the generative ducts of both sides of the body open. 

 In both Decapodous and Hedriophthalmatous Crustacea, the 

 male generative outlet is to be found in relation with the 

 last segments, and the female with the last but two of the 

 ambulatory or abdominal segments. 



n. Coecal sac, the rudiment of the yolk-sac of the embryo. This 

 sac is apparently the homologue of the two coeca, which in 



