MUSEUM OF COMPARATIVE ZOOLOGY. 221 



reo-ion of a special stellar structure, which extends in all directions 

 from the pronucleus, and which has a separate origin from all the 

 stellate structures connected with the production of the polar globules. 

 To this star has been given the name (Fol, 77% p. 360) male aster. 

 It therefore seems remarkable that this structure, which I have called 

 the male pronucleus in Limax, should not be accompanied by some trace 

 of the characteristic star. This would have afforded grounds for appre- 

 hension lest my interpretation of this nuclear body might be erroneous, 

 were it not that the structure of the body, and its deportment under the 

 influence of reagents ; its growth, ever parallel to that of the female pro- 

 nucleus ; its migration toward, and finally its contact with, the latter, 

 pointed unequivocally to its nature as the male element. In no case, 

 by whatever method treated, was any trace of such a stellate structure 

 in the protoplasm surrounding the male pronucleus to be detected, 

 either in its earlier or later stages, although carefully sought for in all 

 the numerous specimens of this age which have come under my observa- 

 tion.* 



It is, therefore, a matter of interest, that a single egg (Fig. 81), which 

 must probably be considered abnormal, should afford the only trace of 

 what is so common to the male pronuclei of eggs in other animals. In 

 this specimen, beside an extensive system of delicate rays which cen- 

 tres near an irregular body that may possibly be the female pronucleus, 

 there are no less than half a dozen other systems of rays, varying some- 

 what in size, distributed through the protoplasm of the vitellus in such 

 a manner as not to be very close to one another, nor yet very near to 

 the surface of the yolk. Each of these smaller stellate figures is com- 

 posed of a few prominent short rays, directed toward a central, homo- 

 geneous body of small size. After studying the observations of Hertwig 

 and Fol (77% p. 469), it cannot be doubted that this is probably a 

 case in which numerous spermatozoa, instead of a single one, have 

 effected an entrance into the egg^ and that their number must have been 

 at least as great as that of the observed smaller stars, whose central cor- 

 puscles may therefore be considered incipient male pronuclei. In the 

 immediate vicinity of the largest aster are to be found two or three 

 other nuclear elements, of which certainly one, and possibly two, occu- 

 pies the centre of its own special system of rays, now considerably ob- 

 scured by the predominance of the larger system with which it has 

 become confused. In the case of the nearer one, the appearance is much 

 as though a union with the female pronucleus were being effected. The 



* The only possible exception has been explained above, p. 220. 



