: 42 Introduction to Am?nal Morphology. 



Poecilopoda the ovary consists of long, tortuous, 

 branched, and anastomosing tubes, those of the two 

 sides united medially. In Isopods the ovary is long, 

 saccular, with a median oviduct. In Oniscus the tes- 

 tis consists of three pair of pouches, which unite into 

 one pair of vesiculae seminales. Mysis and Decapods 

 have a median ovary, with two large, lateral, saccular 

 (Mysis), or lobate oviducts : these open at the base of 

 the third pair of feet. In Anomoura the testes are ab- 

 dominal. Some Stomapods have lateral pouches from 

 the median ovary, and two or more oviducts which 

 unite at a common sexual orifice. In Cirripedia and 

 some Copepods, pigmy or complementary males are 

 developed, with no digestive organs,* like those in 

 Rotatoria. The spermatozoa may be globular (Phyl- 

 lopoda), flattened (Palaemon), crescentic (Cladocera), 

 thread-like (Argulus), radiated (Decapoda), sometimes 

 dimorphic (Isopoda), and either amoeboid or motion- 

 less. In Cyclopsine, Branchipus, &c., the antennae of 

 the males act as claspers. 



In development the ova may undergo complete di- 

 vision, with no primitive streak, and form a larva or 

 Naiiplhis, with an oval body, one eye, and three pairs 

 of limbs. In higher forms the cleavage is only partial, 

 a primitive streak forms from which the germ lamel- 

 Ise extend, inclosing the unsegmented food yelk ; the 

 young becomes a Zoea with a spinose carapace, paired 

 eyes, and post-abdomen. Sometimes both the Nau- 

 plius- and Zoea-stages are gone through before emer- 

 gence from the ^%%. 



* Complementary males are developed in the heiTnaphrodite forms 

 Cryptophialus, Alcippe, &c., as in the dioecious forms, as Ibla, Scalpellum, 

 &c. The male of Limnadia Hermanni is unknowm. 



