178 M. E. Claparede on the Formation of the Egg 



megalocephala, which is probably very similar to the above- 

 described epithelial coat in Ascaris suilla. 



In Ascaris mystax the epithelium presents nothing of the 

 kind ; it is rather perfectly smooth, and Nelson* has described 

 and figured it very accurately. Notwithstanding the opposite 

 statements of Bischoff and Leuckart, we have been unable, any 

 more than Nelson, Meissner, and Thompson, to convince our- 

 selves that the so-called epithelial conules ever adhere to the 

 wall. 



The outer surface of the tunica propria is clothed with a con- 

 tractile layer in the lower part of the genital tube. In many 

 species [Ascaris suilla, A. mystax, Oxyuris vermicularis, &c.) 

 this layer consists of readily perceptible muscular fibres. In 

 other species it appears to be perfectly structureless or simply 

 granular, as Meissner has already remarked with reference to 

 the uterus of Mermis nigrescens and various species of Gordius. 

 Sometimes, however, as, for example, in Cucullanus elegans, an 

 indefinite arrangement of the granules in transverse rows may 

 be detected, from which we may very easily be led to suppose 

 that these rows of granules represent difficultly visible muscular 

 fibres. It was nevertheless impossible to prove the existence of 

 these supposed muscular fibres by means of reagents. 



Lastly, we should mention the granular longitudinal folds of 

 the vitellogene in Ascaris mystax, which also occur in A. suilla. 

 But as Nelson has connected these folds with the yelk-formation, 

 we shall pay attention to them when we come to speak of the 

 formation of the yelk. 



The male genital tube is exactly of the same histological 

 nature as that of the female, except that in the male Ascaris 

 suilla the processes of the epithelial cells are wanting. In an 

 Ascaris from the intestine of Lota vulgaris, which we regard as 

 A. mucronata, the muscular layer consists of fusiform cells, 

 which resemble the smooth muscular cells of the higher animals. 

 Each cell is furnished with a nucleus of as much as 0*016 millim. 

 in diameter, containing numerous nucleolar corpuscles. The 

 portion of the male genital tube of Ascaris suilla which corre- 

 sponds with the vitellogene of the female, is, like the latter, 

 provided with granular longitudinal folds. 



We will also mention that from three to four large oval cells 

 occur at the base of the spicula in certain Nematoidea. Their 

 signification is still perfectly problematical. Perhaps they must 

 be regarded as simple glands. Such cells were found, for ex- 

 ample, in Ascaris suilla, in which they even attain a length of 

 0*23 millim. In Ascaris mucronata they are about 0*18 millim. 

 in length, but slender. According to an oral communication 

 * Reproduction of Ascaris mystax. Phil. Trans, part ii. 1855. 



