242 whitman: ' [Vol. I. 



of the opinion that, under perfectly normal conditions, the sper- 

 matic body remains inactive and stationary at the surface of the 

 egg until the polar globules are excluded/ 



In the case of the teleostean ^^^^ I have positive proof, not 

 only that the spermatozoon enters the egg before any polar 

 globule is formed, but that the pronucleus derived from it 

 attains a central position before the female pronucleus begins to 

 move. 



In the Hirudinea, Biitschli (21, p. 5) and Hertwig (i, p. 30) 

 failed to find the male aster before the appearance of the first 

 polar globule, and my earlier efforts were equally unsuccessful. 

 I have since succeeded in finding a distinct male aster in the 

 fresh-laid egg of Clepsine, i.e., from thirty to forty minutes before 

 the first polar globule arises. The aster at this time has al- 

 ready penetrated to a depth of one-quarter or even one-half 

 the radius of the egg, and is soon after found at, or near, the 

 centre. I am unable to say positively whether it advances 

 somewhat from this position to meet the female pronucleus, but 

 the appearances indicate a slight movement of this kind. The 

 phenomena of fecundation in the Hirudinea, so far as at 

 present known, accord with the conclusions already set forth. 



With reference to Ascaris mcgaloccphala, Oscar Hertwig 

 (11, p. 282) makes the following somewhat surprising remark: 

 " Hier bleiben die grossen Samenkorper, welche die Gestalt 

 einer Spitzkugel haben, I'dngere Zcit nacJi iJii'cn Eindringen 

 ganz unverandert in iJircr iirsprilnglicJicn Gestalt in der Eirinde 

 liegen!' The investigations of Van Beneden (9) and Nussbaum 

 (22), cited in support of this statement, unfortunately con- 



' Fol (No. 24, pp. 106-107) states that in those cases where the egg is fecundated 

 before the formation of the polar globules is completed, the male pronucleus remains 

 at the edge of the vitellus in the condition of a small, immobile, and hardly visible 

 spot until the moment when the elimination of those globules is accomplished. Both 

 pronuclei then arise simultaneously, and each takes its own independent course 

 towards the centre. The place of tneedng, however, is between the centre and the 

 formative pole, because the male promicleus advances more rapidly. It is to be 

 remembered that, under normal conditions, the female pronucleus is formed before 

 fecundation; and, further, that the male pronucleus, in the cases referred to, started 

 from, or near, the nutritive pole. 



21. O. BuTSCHLl. Studien liber die ersten Entwicklungsvorgange der Eizelle, etc. 

 Frankfurt a. M., 1876. 



22. MoRiTZ Nussbaum. "Ueber die Veranderungen der Geschlechtsproducte 

 bis zur Eifurchung." Arch, f.mik. Anat., 1884. 



