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



and each seems rather to assert positively that the right is on 

 his side. It is to be regretted that the strife has not always 

 been kept within scientific limits, and that passion has too often 

 been allowed free play. By this means errors have certainly 

 been produced, which otherwise might never have arisen. 



A communication upon the subject in question has recently 

 been published by Allan Thompson*, in which the author quietly 

 considers the disputed points, and explains them with great 

 accuracy. We regard this memoir as the best that has appeared 

 upon the fecundation of Ascaris mystax. Thompson, a friend 

 of Nelson's, has borne himself as impartially as possible in the 

 discussion; nevertheless, a confirmation of statements by an- 

 other likewise impartial observer might not appear to be un- 

 desirable, especially as Thompson was not acquainted with 

 Schneider's observations upon the movements of the sperma- 

 tozoa in the Nematoidea, and consequently has not referred to 

 them. But if these observations be generalized, and if we assume 

 that the Amoeba-\\\Q movements of the zoosperms occur in all 

 Nematoidea, it might seem improbable that the thimble-shaped 

 corpuscles, which have been described as the seminal corpuscles 

 of Ascaris mystax by Nelson, Meissner and Thompson, are the 

 true zoosperms. These corpuscles have such a constant form, 

 that we cannot well understand how they should move like 

 AmcebcB, unless the extension and retraction of processes be 

 limited to the flocculent end of the corpuscle. 



1. Histology of the Seamal Tube. 



It is above all things necessary to investigate the tissues 

 occurring in the sexual tube of the Nematoidea more accurately, 

 to enable us to decide the question whether epithelial structures 

 occur, which do or do not agree with Bischofi'^s epithelial 

 conules. 



In the female the sexual tube consists of a membrane which 

 is, at all events apparently, perfectly structureless. That its 

 blind extremity consists of a series of cells fused together, as has 

 been represented by Kollikerf, is certainly an error, the origin 

 of which Reichert J has rightly sought for in phsenomena of 

 diffusion. The blind extremity is not unfrequently much thick- 

 ened. A thickening of this kind occurs almost constantly in 

 Cucullanus elegans, in an undetermined Ascaris from the small 



* Zeitschr. fiir wiss. Zool. vol. viii. part 3. 



t Beitrage zur Entwicklungsgeschichte wirbelloser Thiere. Muller's 

 Archiv, 1847. 



X Beitrag zur Eritwicklungsgesch. der Saraenkorperchen bei den Ne- 

 matoden. M tiller's Archiv, 1847- 



