710 JOHN BEARD, 



"Probably the conditions for the development of the one sex or 

 the other are already laid down (gegeben) in the ovarian egg" ^). 



The like results are stated somewhat more fully on p. 522, and 

 it is also recognised, that in the male element, the spermatozoon, the 

 determination of sex (Bedingung des Geschlechts) does not lie. 



Though quite on the lines of certain of the results of the present 

 writing, one error underlies Prof. Schultze's conclusions. It is that 

 double monsters and like-twins must arise from a single egg, con- 

 taining two germinal vesicles. This erroneous assumption 

 was a very natural one to make: it has only now been proved to be 

 unnecessary by my recent work ^) on the germ-cells. If two primary 

 germ-cells commence development within the same developmental 

 foundation, the necessary larva or phorozoon, the conditions 

 are. given either for the formation of a double monster, or for the 

 production of identical twins. 



That Schultze's work has in this long interval borne no fruit 

 is proved by the nature of existing embryological opinion : that it 

 was undoubtedly in the right direction may presently be demonstrated. 



Weismann's recent contribution ^) on the parthenogenesis of bees 

 was published in the number of the Anatomischer Anzeiger, con- 

 taining the resume of my work ^) on the germ-cells. Any connection 

 between the two is apparently only a negative one; but it would have 

 become positive, had I not kept back some of my conclusions. 



The suspicion, which long amounted almost to a certainty, has 

 at last been confirmed for the smooth skate. Raja hatis. With the 

 facts, relating to the primary germ-cells of both male and female 

 skate before me, and with the resolution of the life-cycle of the germ- 

 cells into one of unicellular organisms, that is, into correspondence 

 with the life-cycles of many Protozoa, as indicated in my previous 

 publication, it is at length possible to carry back the solution of the 

 sex-question almost to its final limits, if not quite thereunto. 



1) Recently the view of the ovarial determination of sex has been 

 advocated by A. Rauber (Das Greschlecht der Frucht bei Graviditas 

 extrauterina, in: Anat. Anz., V. 17, 190Ü, p. 455—457). See also: 

 Raubek, a., Der Ueberschuss der Knabengeburten und seine bio- 

 logische Bedeutung, p. 1 — 220, Leipzig 1900. From his experiments 

 Pelüger also concluded, that sex must be decided in the ovary. 



2) Beaed, J., The morphological continuity of the germ-cells in 

 Raja batis, in: Anat. Anz., V. 18, 1900, p. 465—485. 



3) Weismaxn, August, Ueber die Parthenogenese der Bienen, in: 

 Anat. Anz., V. 18, 1900, p. 492—499. 



