24 



THÉEL, HERMAPHRODISM IN HOLOTHDRIDS. 



Hamann,^ Semper'-^ and several other eminent naturalists 

 have stated, that in several Holothurids an albuminous "zona 

 radiata" becomes formed from the ovum. My own experien- 

 ces show that this is not the case in Mesothuria intestinalis. 

 In vain did I search for a zona radiata, in fresh genital tubes 

 as well as in fixed ones. 



However, to judge from preparations stained with iron- 

 hsematoxyline in conformity to the method of Haidenhain, it 

 is evident that the peripheral layer of the ovum sends out a 

 number of large and irregular pseudopodia-like processes which 

 taper towards their free ends and ramify, certainly in order to 

 be capable of absorbing the greatest possible amount of nn- 



Part of a section through an egg treated with iron-hsematoxyline according 

 to Haidenhain. y, yolk; /, follicular membrane; ps, pseudoponia-like proces- 

 ses. Highly magnified. 



Part of a section of another egg stained in the same way. y, yolk; f, folli- 

 cular membrane; p, pellicles. Highly magnified. 



triments from without. They never give rise to a finely radia- 

 ted appearance resembling a zona radiata. 



When studying somewhat thicker sections, I not seldom 

 observed that, instead of finely branched protrusions, fine 



1884. 

 1868. 



^ Beiträge zur Histologie der Echinodermen. I. Die Holothurien. Jena 

 Reisen im Årchipel der Philippinen. II, 1. Holothurien. Leipzig 



