282 [October, 



The last European writer on this subject is Mr. Ed. Grube,* who has made 

 some observations on the development of the eggs of Gordins aq7iaticus, and 

 described a new species from Africa. His paper bears chiefly on minute para- 

 sitical nematoids. He also alludes to the great resemblance there is between 

 Mermis albicans and Ascaris acuminata. 



III. 



The anatomical structure of Gordiaceas is also a matter of much controversy 

 amongst anatomists. 



Prof Sieboldjf in giving an account of the difference between intestinal worms 

 and Gordii, again calls the latter enigmatic. 



Bertholdl describes a system of circulation, neither seen nor acknowledged by 

 the authors that came after him. He likewise mentions a nervous system ; but 

 giving no further account of it, its characters and distribution in the body of these 

 worms remain to be investigated. 



Dujardinll is in a complete doubt. 



Prof. Siebold, in resuming Berthold's and Dujardin's investigation, says that 

 the organs which Berthold took for veins and arteries, are contracted fibres, and 

 that he has failed of seeing any organs which he could confidently call nervous or 

 vascular systems. 



We do not know yet the digestive tube of any Gordiaceae. One fact, however, 

 is ascertained with regard to that organ: it atrophies in full grown indi- 

 viduals. Even the structure of the skin, or external envelope of the body, 

 deserves a more full coi iparative study. 



Although Charvet and Berthold agree in saying that Gordiaceas are androgynous, 

 it has been plainly ascertained since, that the sexes are distinct. But the struc- 

 ture of the sexual organs is not known. Prof. Siebold found an external charac- 

 ter by which males differ from the females, the former, in G. aqiiaticics, having 

 a bifurcated tail. 



IV. 



Some observations on the development of the eggs of Gordius aquaticus have 

 been made by Ed. Grube.lT Dr. Joseph Leidy had made similar investigations in 

 1846, and published only in 1850.** The eggs are laid in strings, nearly of the 

 length, and sometimes the color, of the worm itself. Within those whitish strings 

 or cords are found the eggs. The division of the yolk takes place, according to 

 the general law of division of that substance, previous to the formation of the 

 embryo. The embryo itself is gradually formed out of the yolk's substance, in a 

 manner similar to that in Clepsinae, and leeches in general. The young resemble 

 their parents as soon as hatched. 



* Tiber einigen Anguilulen und die Entwicklungs. von Gordius aquaticus. 

 Trosch. Archiv fiir Naturgeschichte 1849, vol. i.p. 358. PI. vii. 



j- Wiegman's Archiv, 1838, vol. iv., i. p. 302. 



jUeber das Bau das Wasserkalbs, 1842, in 12. 



II Annales des Sciences Naturelles. 2de serie, vol. xviii., 1S42, p. 142. 



Wiegma.}t's Archiv, 1843, ii. pp. 302 and 307. 



ir Troschel fiir Naturgeschichte, 1849, i. p. 358. PI. vii. 



Notes on the development of Gordius aquaticus. Proc. Acad. Nat. Sci., 

 Philad., 1850, p. 89. 



