The determination of sex in animal development. 709 



many theories of sex, leanings towards metaphysics — a subject, 

 which is the very antithesis of morphology. In possessing a morpho- 

 logical basis the new features to be recorded concerning sex differ i n 

 toto from previous explanations. The present account merely points 

 out the material basis of what we term "sex", and in itself it does 

 not pretend to furnish indications how this can artificially be controlled 

 or modified 1). Anything of this nature is, of course, a question for 

 physiology, and not for morphology. 



Whilst I was engaged in putting together an account of my results, 

 two publications, the one botanical, the other zoological, appeared. 

 Weismann's writing treats of the determination of sex in the partheno- 

 genetic development of the bee's egg, Strasburger's with the like 

 question in dioecious plants. The results and conclusions of both 

 observers will be referred to in the sequel. 



Without attempting to give an account of previous inquiries and 

 theories, one matter must be brought forward. The investigator owes 

 a debt of gratitude and recognition to those, who have gone before 

 him. His debt is all the greater, when the interval of time between 

 their work and his own is a long one. And it still exists, when in 

 any way — even in the enunciation of an idea — they may have 

 anticipated something in his results. 



Between the present writing and suggestions allied to the con- 

 clusions contained in it there lies an interval of nearly fifty years! 

 In 1854 Dr. Bernhard Schultze-) from the consideration of the 

 phenomena presented by double monsters and like-twins rightly drew 

 certain conclusions. 



His results (p. 527) include: 



"All double monsters arise in one egg." 



"In a single mammalian egg there invariably develops only the 

 one sex, male or female." 



1) At the same time I would insist, in agreement with Stkas- 

 BURGER (in: Biol. Ctrbl., V. 20, 1900, p. 785), that to all appearance 

 any alteration of the relative numbers of the two sexes experimentally 

 is an impossibility. In the present writing the experiments of Yung, 

 Born, Maupas , Mrs. Treat , and others have received no mention, 

 because at the best their researches only prove what percentage of either 

 sex will survive under given conditions. 



2) ScHULTZE, B., Ueber anomale Duplicität der Axenorgane, in : 

 Arch. path. Anat., V. 7, 1854, p. 479—531, 1 pi. 



