CRUSTACEA. 



329 



The female organs present, like the male, a progressive com- 

 plication of structure as the species ascend in the class. Most of 

 the small Entomostraca carry the impregnated ova in appended 

 ovisacs, like those of the Lernege. These sacs are not developed in 

 the Limulus, which also differs from the smaller Entomostraca 

 inasmuch as the ovarian mass interblends its lobes and processes 

 with those of the liver ; the oviducts form more frequent com- 

 munication with each other than in the higher Crustacea, but ulti- 

 mately terminate, like the vasa deferentia, by two distinct but 

 contiguous orifices on the back part of the first abdominal lamelli- 

 form appendage. 



The ovaria in the lobster are of great length on each side ; the 

 oviduct comes off from the outer part of nearly the middle of the 

 gland, and descends to terminate at the basal joint of the third pair 

 of ambulatory feet. 



In crabs the female apparatus reaches its highest state of compli- 

 cation, and consists of an ovary, oviduct, and a copulatory pouch, or 

 spermatheca, on each side. The ovaria are elongated cylindrical 



sacs in the Maia {Jig. 135), and 

 are divided into an anterior («) 

 and a posterior part {h), the short 

 oviduct {d) being continued from 

 the union of the two : the anterior 

 parts of the ovaria are united 

 together by a short transverse 

 canal {a') ; the posterior divisions 

 are intimately united through half 

 their extent ; the spermatheca (c) 

 is developed a little above the ter- 

 mination of each oviduct ; and the 

 spermatophora and spermatozoa 

 in this receptacle afford favour- 

 able subjects for microscopic obser- 

 vation. 



The species of a genus of Mac- 

 roura {3Ii/sis) are called " Opossum shrimps " from carrying their 

 ova during the process of development in abdominal recesses, an- 

 alogous to the marsupial pouch ; but this superadded complexity 

 in the reproductive economy is common, under various modifi- 

 cations, to all the Crustacea. 



The wider our survey of living nature extends — the greater the 

 number of facts in the history of animals with which we become 

 acquainted — the more do the points of correspondence between the 



Female organs, Maia Squinndo. 



