Journal of Applied Microscopy. 337 



Carnoy and Lebrun's Observations on Fertilization in 

 Ascaris Megalocephala. 



The true interpretation of the process of fertihzation is fundamentally neces- 

 szry to the solution of many problems of heredity. Observation has not yet 

 settled conclusively the ultimate fate of the constituents of the spermatozoid or 

 the part they play in this process. The least light on this subject ought there- 

 fore to be of far-reaching interest. 



Ascaris megalocephala, on account of its large spermatozoa and few chro- 

 mosomes, is a most favorable object for the study of fertilization, and indeed 

 has become classical : but widely different results have been reached, varjdng 

 with the methods employed. The technical difficulties involved hinge about 

 fixation and embedding. Flemming's fluid, Hermann's, nitric acid, sulphurous 

 alcohol, and many other killing fluids of unquestionable value elsewhere fail at 

 the dense &^^g membrane of the nematode. Carnoy and Lebrun, in their paper 

 which appeared in " La Cellule " nearly two years ago, report the excellencies of 

 Gilson's fluid, which is composed of equal parts of glacial acetic, chloroform, and 

 absolute alcohol with corrosive sublimate to saturation. The glacial acetic has 

 a softening etTect on the &gg covering ; the chloroform, being woxy rapidly pene- 

 trating, is said to anesthetize the protoplasm ; while the other two constituents 

 fix ver}^ promptly and very faithfully the different cell structures. In their use 

 of this fluid unusual precaution was taken to insure its full effect by slitting the 

 uterine tubes in many places. Having acted for some ten minutes, the fluid was 

 followed by weak alcohols, until all traces of acetic and chloroform odors had 

 disappeared, then by increasing alcohols to eighty per cent, where the material 

 w^as preserved. Embedding in paraffin of a melting point below 5(i° C, after 

 immersion for one to two minutes at most, was the only admitted alternative 

 with the much preferred celloidin method. Three changes (of increasing thick- 

 ness) of the latter, each used for fifteen days, were found necessar}^ Staining 

 was by Heidenhain"s iron haematoxylin method. 



Taking up fifst the phenomena of maturation, they attack the problem of the 

 nature of the polar figures — whether they are true ki)ieses, as that term is gener- 

 ally understood. The view most widely accepted may be summarized after 

 Sobotta as follows : (1) no centrosomes in polar figures ; (li) no true asters : 

 (3) spindle truncated — fibers not meeting at the centrosome. Boveri and 

 Sobotta hold that there could be no centrosome in the maturing ovum because 

 it has already been lost from the cytoplasm of the ovocyte, and this essential 

 element will be lacking until it is supplied by the entering spermatozoid. 

 Lebrun's discovery of "polar corpuscles" or centrosomes in Ascaris (lsll2) has 

 been confirmed by Haecker, Sala, v. Erlanger, and others. The authors claim 

 for Gilson's fluid the preservation of aster rays, though not so distinct as in 

 ordinary- kineses. They thus supply another element of a true kinesis ; and 

 they oppose the deduction of Sobotta, that because the spindle is not pointed it 

 is therefore not a true one. 



