20 



The Microscope. 



bility. It starts with the supposition that each cell is originally 

 neither male nor female, but rather that it contains both ele- 

 ments. The process is diagram matically shown in the adjacent 

 cut, adapted from Minot. a represents a germinal cell contain- 



Fig. 3. — Diagram of modifications of an originally simple cell, a\ b, elim- 

 ination of male element (polar globules) to form the egg; b, pro- 

 duction of spermatozoa, the female portion of 

 the cell being left behind. 



ing both sexual elements. In the egg (b) the pronucleus, or 

 male element, has escaped, and the egg is now exclusively 

 female. In c the spermatozoa are escaping from the germinal 

 cell, leaving the female portion behind. 5, as will readily be 

 seen, represents the egg with the female pronucleus found. 



From this it would seem that the egg in order to be fertil- 

 ized needs to get rid of the male element, which originally be- 

 longed to it, and that a new male element was necessary. 

 There is one series of facts which has its bearing upon this 

 hypothesis, which may be mentioned here. In almost every 

 group of the animal kingdom the formation of polar globules 

 has been witnessed except among the arthropods and rotifers, 

 where (he evidence in favor of their production is as yet very 

 slight. Here is a point for investigation. Are polar globules 

 formed in either of these groups ? Now it is a peculiarity of 

 these two groups that here alone does parthenogenesis occur. 

 Eggs of both insects and rotifers have again and again been 

 known to develop without the presence of the male element or 

 spermatozoa. It is therefore at least plausible to suppose that 

 that portion which is expelled in other groups, by being retained 

 here is sufficient to cause the egg to develop. Whether subse- 

 quent researches will confirm this idea cannot be foretold, but 

 the speculation is at least an interesting one. 



