1884.] 57 [Hyatt. 



suggests in his Comp. Embryol. vol. i, p. 62, that the capacity 

 for parthenogenetic development may be dependent upon the 

 expulsion of the polar globules, and adds that "strong support 

 for this hypothesis would be afforded were it definitely estab- 

 lished that polar bodies were not formed in the Arthropoda and 

 Rotifera," which are extensively parthenogenetic. 



The apparent contradictions to the gonoblastic theory which 

 may be found in the absence of true polar globules in the forms 

 mentioned and in others, are not, as often supposed, fatal to the 

 hypothesis. If it be true, that the nuclei become differentiated, 

 in spermatocysts and ova and in the bodies of Protozoa, into 

 two parts which may be properly termed masculo- and femino- 

 nuclei, and, if these parts have distinct sexual functions, so that 

 the union of the products of the masculonuclei of spermatocysts 

 with the feminonuclei of ova is necessary in order to form 

 segmentation or maritonuclei, the gonoblast theory is reliable, 

 otherwise it fails. What may become of the useless or super- 

 fluous feminonuclei of the spermatocysts or the equally useless 

 masculonuclei of the ova is evidently not vital to the explan- 

 ation, nor is it essential, as we claim, that the expulsion of the 

 polar globules should as a rule take place earlier in the Metazoa 

 than the resorption or exclusion of the useless parts of the 

 nucleus in the Protozoa. We have in other publications tried 

 to give the evidence with regard to the law of earlier inheritance 

 and think it should be applicable to such phenomena, if it has the 

 wide application which has been claimed for it, but it is not a 

 necessity of the gonoblastic theory. 



This law certainly seems to give a plausible answer to such 

 objections to the gonoblastic theory as have been made by Dr. 

 Whitman in his review of this theory in his paper on the embry- 

 ology of Clepsihe (Quart. Journ. Micr. Sci. n. s., vol. xvin, 1878.) 

 This author regards the agamic nature of the origin of the polar 

 globules as contrary to the hypothesis, whereas if we are right 

 in our translation of the laws of heredity the reverse is true and 

 since the Metazoa are descendants of Protozoa the globules 

 should tend to appear earlier or previous to impregnation in the 

 ova. We are aware that this is setting up one hypothesis to sup- 

 port another, but it will be remembered we hope by just critics, 

 that the law of acceleration and concentration in development 



