172 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Castration and Growth of Bone.* — H. Sellheim finds that castration 

 of ox, horse, sheep, goat, dog, fowl, in buth sexes prolongs the period 

 of bone-development, and has thus an effect on the shape of various 

 parts. 



Is there Parthenogenesis of the Microgamete in Metazoa ? | — 

 Prof. A. Giard suggests that the phenomena observed by Delage, and 

 termed " merogonic," where a non-nucleated ovum-fragment, fertilised by 

 a spermatozoon, proceeds to develope normally, may be regarded as cases 

 where the microgamete or sperm-cell developes parthenogenetically. 

 Siedlecki % has observed the parthenogenetic development of the micro- 

 gamete of the sporozoon Adelea ovata ; and the same, as Klebs and others 

 have shown, may occur in the lower plants. If this be the true inter- 

 pretation of merogonic development, one would expect that the resulting 

 organism should he like the mala which furnished the spermatozoa, a& 

 might be tested, on the lines of Boveri's famous experiments, where the 

 ovum and sperm belonged to distinct species. It may be, however, that 

 the cytoplasm of the ovum will modify in some measure the expression 

 of the hereditary characters in the sperm. 



In some cases Delage found more embryos developing from fragments 

 than from an equal number of intact ova in the control experiments. It 

 is suggested that this may be explained by the intense phagocytic power 

 of the immature ova, which engulf not only follicular cells but sperma- 

 tozoa as well.§ In the case of the fragments, the absence of the nucleus 

 prevents the assimilation of spermatozoa, and therefore facilitates fertili- 

 sation and development. 



Giard's way of looking at the facts may also throw some light on the 

 phenomena observed by A. Millardet,|| in his " Note sur l'hybridation 

 sans croisement ou fausse hybridation," where the hybrid (strawberry- 

 plants, &c.) reproduced exclusively the paternal type. For it may be 

 that for some reason the female pronucleus had in these cases degene- 

 rated, and that the " false hybrid " was the result of a parthenogenesis 

 of the male element. The author applies the same idea to Heron- 

 Iioyer's U experiments on hybridising amphibians, where the paternal 

 characters predominated in the offspring. 



[It may be suggested, however, that these are simply cases of pre- 

 potency on the part of the male parent, which may be re-expressed in 

 terms of germinal struggle between the paternal and maternal determi- 

 nants, without any hypothesis of sperm-parthenogenesis.] 



Experimental Embryology.** — Dr. V. Haecker fiuds that the de- 

 veloping eggs of Cyclops exposed for 2-3 hours to the influence of 5 per 

 cent, ether solution show in their nuclear divisions phenomena like those 

 of amitosis. After the ether is removed, the nuclear divisions take place 

 after the normal mitotic type. He leaves it an open question whether 



* Beitr. Geburtshilfe Gynakol., ii. (1899) pr. 236-59. See Zool. Centralbl., vii. 

 (1900) p. 10G. f Reprint from C.K. Soc. Biol. Paris, 1899, 4 pp. 



% Ami. lust. Pasteur, 1899, pp. 170 and 180. 

 § See Iwanzotl, Bull. Soc. Nat. Moscou, 1898, pp. 355-67. 

 || Mem. Soc. Sci. Bordeaux, iv. (1894). 

 1 Bull. Sec. Zool. France, viii. (1883) pp. 397-416. 

 ** Anat. Anzeig., xvii. (1900) pp. 9-20 (16 fi^s.). 



