SPECIAL SUBJECTS. 
Gen. Sub. 33 
Hertwfg, R. Ueber Polyspermie. S.B. Ges. Morph, ii, pp. 1-4. 
Hertwig, O. & R. Experimentelle Untersucliungen liber die Beding- 
ungen der Bastard befruchtungen. Jen. Z. Nat. xix, pp. 121-165. 
(1) The success of hybrid fertilisation does not wholly depend on the 
degree of relationship ; (2) it is frequently not reciprocal ; (3) the state 
of the elements is an important condition. The various results de*pend 
almost exclusively on the plasticity of the ovum. The hybrid fertilisa- 
tion occurs the more readily the livelier the sperms, the weaker the ova. 
The vigorous ovum is the seat of regulative forces which guarantee 
normal, and hinder hybrid and polyspermie fertilisation. These are 
efficacious in proportion to the general vitality of the ovum. 
. Experimentelle Untersuchungen uber Bef ruchtung. Anat. Anz. i. 
pp. 11-16; J. R. Micr. Soc. 1887, pp. 44 & 45. 
Effect of chloral hydrate on fertilised ova of Strongy.locentrotus lividus 
— hinders .normal conjugation of the nuclei. Maturation and fertilisa- 
tion are associated with fundamental protoplasmic changes. 
Horst, R. Zur Regenerations litteratur. Zool. Anz. ix, p. 50. 
Hyatt, A. Larval Theory of the Origin of Tissue. Am. J. Sci.pp. 332- 
347 ; Ann. N. H. xviii, pp. 193-209. [Of. P. Bost. Soc. 1884.] 
As in 1884, “ tissue cells of Metazoa are similar to asexual larvae, and 
are related by their modes of development to the Protozoa." 
Jaworowski, A. [See Cell.] 
Rapid death of Chironomus after reproduction due to repletion of 
abdominal cavity with blood after expulsion of elements. Paedogenesis 
due to rupture of the incompletely developed ovarian membrane and the 
liberation of ovules into the body cavity, where, in richly nutritive 
environment, they are able to develope into larvae without fertilisation. 
Jhering, H. v. Generationswechsel in Saugethieren. Biol. Centralbl. 
' vi, pp, 532-539 ; J. R. Micr. Soc. 1887, p. 44. 
In Praopus eight embryos from one germ. Notice of other cases. The 
origin of multiple embryos from a single ovum is the primitive condi- 
tion, the development of only one is secondary and adaptive. Revised 
scheme of modes of reproduction. I Hologenous : fertilised ovum 
developes, with or without metamorphosis, into a single individual, 
ii Merogenous ovum forms two or more individuals (a) like parent in 
structure and reproduction— temnogenesis ; ( b ) metagenesis, (1) calyco- 
genesis in Salpce and Medusas, (2) paedogenesis in Cecidomyias , (3) hetero- 
genesis, with both generations sexual, or one or several parthenogenetic. 
Jourdain, S. Blastogenese. C.R. ciii, pp. 1086-1088. 
Blastogenesis continuous during whole life of stock ( Botrylloides 
rubrum ) only accelerated in post-larval life. Buds of B.rubrum at every 
stage are hermaphrodite at first. In cold season both glands atrophy ; 
later on, male gonad alone persists ; in warm weather, both kinds of 
gonads completely developed. 
