ACANTHOCEPHALT 255 



cavity. If then, provided we rightly understand K\iser's statements, a 

 union of two plates were to take place dorsally and ventrally, the re- 

 semblance to mesenteries would indeed be strong. The plates could 

 certainly arise only from the above-mentioned third or inner layer, which 

 separated from the central mass at the time of the formation of the body- 

 musculature. The two outer layers would then be applied to the body- 

 wall, whereas the inner layer would perhaps assume the formation of 

 the internal organs, the proboscis-sheath, and the ligament, in some 

 such manner as was described by Leuckart. This is the way at least 

 in which we should interpret the statements of Kaiser in the absence of 

 his more detailed descriptions. 



In regard to the origin of the genital organs, especially the extensive 

 conducting apparatus, we refer to Kaiser's communication, or, better still, 

 to the awaited complete work, for it cannot be determined from the 

 former what is the real origin of those elements which constitute the 

 genital apparatus. 



The Echi7iorhi/nchus, which even in the body of the inter- 

 mediate host attains in general the form of the adult worm, 

 becomes capable of reproduction only when the animal 

 harboring it is consumed by another which is adapted 

 to serving it as permanent host, thus, for example, the 

 Gammarus by a fresh- water fish or a duck, if the species be 

 Echinorhynchus polymorplius. 



Literature. 



1. Greeff, E. Untersuchungen iiber den Bau und die Naturgeschichte 



von Echinorhynchus miliarius (E. polymorphus). Arch. Natuig. 

 Jahrg. xxx., Bd. i. 1864. 



2. Kaiser, J. Ueber die Entwicklung des Echinorhynchus gigas. Zool. 



Aiizeiger. Jahrg. x. 1887. 



3. KoHLER, K. Documents pour servir a I'histoire des Echinorhynques. 



Journ. Anat. et Physiol. Tom. xxiii. 1887. 



4. Leuckart, E. Die Parasiten des Menschen, etc. Bd. ii. Leipzig. 



1876. 



5. MectNin, p. Eecherches sur I'organisation et le developpement des 



Echinorhynques. BvlL Soc. Zool. de France. Tom. vii. 1882. 



6. Safftigen, a. Zur Organisation der Echinorhynchen. Morph. 



Jahrb. Bd. x. 1885. 



Appendix to Literature on Acanthocephali. 



I. Hamann, 0. Die Nemathelminthen. Beitrage zur Kenntniss ihre 

 Entwicklung, ihres Baues, und ihrer Lebensgeschichte. Jena. 

 Zdtschr. Bd. xxv. 1891. 

 II. Kaiser, F. Die Acanthocephalen und ihre Entwicklung. Bibliotheca 

 Zuologica. Heft 7. 1893. 



