122 



THE IIELMIXTilES. 



§115. 



In the terminal, constrictel portion of the uterus, eggs, vitelline cells, 

 and spermatic particles are often found mixed together. It is probably here 

 that the eggs are formed, their fecundation occurring without copulation, 

 and by means of the Vesicula seminalis interior. The succeeding folds of 

 the uterus contain already, nicely-defined, oval eggs containing a germ and 

 many vitelline cells. Their recently-formed envelope is still colorless, and so 

 thin and flexible, that the peristaltic contractions of the uterus give it a 

 variety of forms. But in passing from the uterus they lose this flexibility ; 

 their envelope becomes more solid, — of a yellow and then a brown color ; 

 and the whole, at the same time, undergoes a decrease in size, due prob- 

 ably to a condensation of their substance. The eggs of most of the Trema- 

 todes have an opercular opening at one extremity. ^^^' 



In the Gestodes, the walls of the genital organs are so very thin, and so 

 intimately blended with the parenchyma of the body, that their structure 

 and relations have not yet been well made out. 



With the exception of in Caryophyllaeus,^-^^ these organs are repeated many 

 times one after another, having in the same individual difi"erent degrees of 

 development. They are always most complete in the posterior portion of 

 the body, being only rudimentary near the neck, while in the neck itself 

 they do not exist at all. In the articulated Gestodes, each ring contains 

 both male and female sexual organs ; and in their two Groups, the arrange- 

 ment of these is the same as in the Trematodes. It is probable that the 

 ovaries and the secreting organs of the vitellus are separate.*"^' In Ligula, 

 Triaenophorus, and Bothriocephalus, the uterus consists, exactly as in the 

 Trematodes, of a very tortuous tube filled with oval eggs.'-^^ But in 



the posterior extremity of tlie body. Its position 

 is iudicated, even wlien the penis is not protruded, 

 by a small papilla. 



With Octobotkrium, and Poli/siomum, there 

 is a round muscular sac concealed directly behind 

 this opening, which contains a circle of delicate 

 horny ril)s, the lower extremities of which are 

 bifid and form a support like a bownet. Mayer 

 (Beitr. loc. cit. p. 21, Taf. lit. &g. 3, 6) has seen 

 ten similar ribs with Octobothrium lanceolatum. 

 I have found eijrht with Poly.itoinum intes^erri- 

 iniim, and forty with Polystoinum ocellatum. 

 Tlieir use is wholly unknown to me. 



I'J The eggs of the Trematodes have apparently 

 only a single envelope. Among the normal eggs in 

 the uterus may often be found others which are mal- 

 formed, also very irregular bodies of a yellowish or 

 brown color, formell almost enth-ely of the sub- 

 stance of these envelopes. These bodies were 

 most probably secreted by the walls of the uterus 

 (the Tuba Fallopii) at a time when the ovaries and 

 the secreting organs of the vitellus were inactive, 

 SI that the substatice of the envelopes' was hard- 

 ened bef)re receiving their usual contents. With 

 Amphistomiim siihclavatum, Octobothrium lan- 

 ceolatum, Polystoinum inte/i^crrimum, and ocel- 

 I'ltum, and JJijilnznon paradoxum, the eggs are 

 Vi;ry largt;, and in the last-named species their ex- 

 tremities an! narrowed and lengthened into a spiral 

 filament, wherefore one of these eggs has been taken 

 for a testicle and penis ; see Nordmann Microgr. 

 Ueitr. lift. 1, p. 7:5, Taf. V. VI. fig. 1, h.; also f^ogt, 

 in Müller' s Arch. 18-11, p. 34, Taf. II. fig. 11. 



The eggs of Monoslomum verrucosnm, and 

 gome other species of this genus which live in the 

 iutestiue of Chelonia esculenta, have a very dif- 



ferent form ; they are oval and colorless, and at 

 each extremity have two papillae, which are grad- 

 ually developed into very long, sharp appendages ; 

 see Dujardin, Hist. Nat. d. Hehninth. PI. YIII. 

 fig. G, B. 3.* 



-" With Caryophyllaeus mutabilis, there is only 

 a single cirrhus-sao upon the ventral surface of the 

 posterior body, and from which a deUcate long 

 penis often protrudes. 



21 I think I have seen an ovary in each of the 

 segments of Bothriocepha/us punctatus, and Tae- 

 nia ooellata. As such, ought, perhaps, to be re- 

 garded those organs which E.ichricht (Nov. Act. 

 Acad. Leop. XIX. Suppl. 2, Tab. I. fig. 2, e, e) 

 has considered with Bothriocephalus latus to be 

 ovaries. The organs secreting the vitellus are a 

 mass of irregularly arranged granulations situated 

 upon both the dorsal and the ventral surfaces, and 

 which have very fine excretory ducts. This mass, 

 called by Encliricht (loc. cit. p. 25, Tab. I. fig. 5) 

 the ventral and dorsal granules, cannot, together 

 with its excretory ducts, be made out, excei)t when 

 filled with the vitelline sul)stance. With Taenia 

 ocellnta, the vitelline organs are limited to the 

 sides of each segment, at the anterior border of 

 which two main excretory ducts are easily seen j 

 these form a single short canal in the middle of the 

 body. In this same place are two transversely- 

 jilaced oval sacs, and which are probably the two 

 ovaries. 



22 The uterine convolutions are generally in the 

 middle of the body, and when filled with matm'e 

 eggs, appear through the skin as a brown rosette ; 

 see Eschricht loc. cit. Tab. I. II. {Uotliriocej-ha- 

 lus latus). 



* [§ 115, note 19.] See also for the structure of p. 602, Taf. XX. ft|j 

 the genital organä Tliaer, Müller's Arch. 18ÖÜ, culalum). — üb. 



17 {Polystomum appenJi- 



