254 [6 



der Eikapsel befanden, befruchteten, indem sie ihnen eine kleine Spermamenge beibrachten, die nun 

 bis zur Bildung der Ovarien in der Geschlechtsgegend, d. h. in der Leibeshöhle zwischen Magen und Darm, 

 liegen blieb. Sobald dann die Ovarien sichtbar werden, soll jede der Oogonien bereits je ein Spermato- 

 zoon enthalten. Ganz merkwürdig ist das weitere Verhalten dieser Spermakerne, indem sie sich bei 

 den weiteren 40 — 50 Oogonienteilungen immer zugleich mit dem weiblichen Kern, und zwar ami- 

 totisch wie jener, teilen sollen. 



Über die näheren Einzelheiten dieser Erscheinung und das fernere Schicksal der Oogonien 

 berichtet S h e a r e r folgendes (S. 158): ,, These (gemeint sind die Ovarien) only appear at a much 

 later date, when the female has grown considerably in size. They are seen then as a few small refractive 

 cells in the living state, and as small nuclei surrounded with hardlv any cytoplasm in the stained 

 condition, bcneath the gut and amongst the mass of sperm. Shortly after they appear it is seen 

 that each one is joined by a Spermatozoon, the head of which has become embedded or attached 

 to its nuclear wall, so that ultimately the nucleus of each primitive ovum is seen to be composed 

 of one part derived from the Spermatozoon, and the other part the female portion. These two elements 

 of the nucleus never fuse, but retain their individuality throughout all the öogonial divisions. The 

 double nucleus divides amitoticallv, each half separately. In the majority of the divisions the male 

 and female portions of the nucleus divide equally, so that a similar quantity of nuclear material, 

 both male and female, gets into each daughter cell. There are probably about forty to fifty öogonial 

 divisions in all. In these the male and female portions of the nucleus divide and move apart simultan- 

 eously, the male portion usually dividing first. Now and again, however, the female half of the 

 nucleus seems to divide before the male portion, so that the male portion gets left behind and is shut 

 off entirely in one of the daughter cells. Therefore of the two resulting cells of this division, one 

 has the whole of the male part of the original nucleus and its share of the female portion, while the 

 other has only half the female and no male substance. This appears to be the sex determining factor; 

 for of these two daughter cells, the one that has received the whole of the male element, plus the 

 female element, becomes the female, while that which has received the female portion alone becomes 

 the male. Both these kinds of eggs, once the sex determining division has taken place, grow rapidly. 

 They seem to accomplish this through the power of absorbing and building up into themselves all 

 the other immature egg cells with which they happen to come in contact, and in which the divisions 

 of the two portions of the male and female substance has been equal. The outcome of this process 

 is that the male egg is not fertilized, while the female egg is. It is, however, impossible to speak 

 in the strict sense of the word of the male egg as unfertilized, as it has been directly under the influence 

 of the sperm in all the early öogonial divisions previous to the sex determining one. For all the primi- 

 tive germ cells are joined in the first place by a Spermatozoon, irrespective of the fact that only some 

 of these will give rise to ova later, and that the majority will be only nurse cells. It is only in 

 the late stages, shortly before the female egg is laid, that the two portions of the nucleus, the male 

 and female actually fuse beyond recognition. As the two kinds of eggs, male and female, are not found 

 in a simple ratio, but in the proportion of three or two, to one male, it is probable that some other 

 division takes place in the case of the female egg. I have been unable to decide this point so far, 

 from my sections." 



Demnach würde also das Verhalten von Dinophilus in bezug auf frühzeitige Besamung der 

 weiblichen Geschlechtszellen die bisher bekannten Fälle von Saccocirrus und Otomesostoma bei weitem 



