NEMATODA. 



349 



stage the characteristic oral capsule of the sexually adult stage, to 

 which they only develop in the intestine of the Perch. According 

 to Fedschenko,* a similar mode of development occurs in Filaria 

 medinensis. The embryos pass unto puddles of water, and migrate 

 thence into the body cavity of the Cyclopidce ; and after casting their 

 skin assume a form which, except for the absence of the oral capsule, 

 resembles that of the larva of Cucullanus. After the expiration of 

 two weeks there is another ecdysis, with which is connected the loss 

 of the long tail. The later history is unknown. It has not yet 



FIG. 282. a, Rhabdcnema (Ascarin) n>grovenosiim of about 3'5 mm. in length in the stage of 

 maturity of the male products ; G, genital glands ; 0, mouth ; D, intestine ; A, anus ; N, 

 nerve-ring ; Drz, glandular cells ; Z, isolated spermatozoa, b, Male and female Rhubditis 

 forms from about I'o mm. to 2 mm. long ; Oo, ovary ; T, testis ; V, female genital opening ; 

 Sp, spicula. 



been discovered whether the migration of the Filarian larva into 

 the permanent host (Man, see p. 356) takes place with the body of 

 the Cyclops, or independently after copulating in the free state. 



The embryos of some Nematoda develop in damp muddy earth, after 

 casting their skin, to small so-called Rhabditis forms with a double 



* Compare Fedschenko, " Ueber den Bau und Entwicklung der Filaria 

 medinensis," in the Bericltten der Freunde der Naturwissenschaften in 3foskaii, 

 Tom VIII. and X. 



