556 THE ANATOMY OF INVERTEBRATED AXIMALS. 



continued into the vagina (Fig. 157, C). The uterus passes 

 above into a short, open, funnel-shaped canal, which lies be- 

 tween the two oviducts (Fig. 157, C c), and, according to Von 

 Siebold, takes in the ova from the perivisceral cavity by a pe- 

 culiar swallowing action. 



The embryos of the different species of Echinorhynchi 

 vary somewhat in structure. Von Siebold has described those 

 of E. gigcts^ which are provided w4th hooks disposed like those 

 of the Gestoidea^ but only four in number. Sexless JEchino- 

 rhyjichi have been found in Cyclops and in the muscles of 

 fishes. Leuckart states that they acquire sexual organs in 

 the alimentary canal of Gadus lota. The same excellent ob- 

 server has succeeded in tracing the development of Echino- 

 rhynchus proteus, a common parasite of many river fishes, es- 

 pecially the Perch. ^ What appeared to be the sexless con- 

 dition of the same Echinorhynchus had previously been seen 

 by Leuckart in Gamraarus pulex. Into water containing 

 specimens of this Crustacean, ova from E. proteus were trans- 

 ferred. After a few days these ova could easily be detected 

 in the digestive tube of the Gaimnarus, while numerous em- 

 bryos, escaped from the egg-shell, were found within the ap- 

 pendages of the Crustacean. 



Each ovum has two coats — an outer, albuminous, and an 

 inner, chitinous. The first is digested in its progress through 

 the alimentary canal ; the second is afterward ruptured by 

 the embryo, which bores through the intestinal walls into the 

 cavity of the body, and is thence conve^'ed to the site proper 

 for its development. 



The body of the embryo is somewhat fusiform in shape, 

 and consists of a colorless, transparent parenchyma, protected 

 by a cuticle. The parenchyma may be resolved into an outer, 

 homogeneous, contractile layer, and a semi-fluid medullary 

 substance. Within this is lodged an ovoid, central mass, 

 made up of large, hig'hly-refracting granules. Isolated gran- 

 ules of the same kind may also be found scattered throughout 

 the soft medullary substance. At its posterior end the em- 

 bryo tapers to a point, while its opposite extremity is obliquely 

 truncated toward the ventral aspect. On this oblique surface 

 may be observed two series of straight spines, five (rarely six) 



1 " Ueber Echinorhynehns " (" Gottinc^er Nachrichten," 1862). Results of 

 further investlsrations and a history of the subject are contained in Leuckart's 

 " Prooframm," " De statu et embryonalietlarvali Echinorhynchorura eorumque 

 inetamorphosi," 1873; and, further, in the concludins: part of "Die mensch- 

 lichen Parasiten," 1876, which has reached me too late for use in this place. 



