MA ! \\l> 1'K'M |>, ,,1 1 |.|;| Hi- M [ ,\. 1 .', 



injures tin* i. r u'ivll. 'lhi> may be accomplished eith'.> 

 inu r it t iiiporarily to :i low r or :i liL'ln-r t.-n. ami 



prodiieinir oold-rigor or i r, or i>y affecting it with 



chemical re:ir nts, chloroforming it. or treating i1 with morj. 



Imino, nicot iiif, (jiiiiiiiie. etc., or hv lining vio]t-nco to it in a 



lanical way, such as shaking it. It is interest!] 



witli all of t !> HUMUS, tin- degree of superfetation i<, to a certain 

 '.t, proportional to the derive of tin- injury : h .ample, a 



Mnall number of spermatozoa penetrate into eggs which have 

 slightly affected with chloral, whereas a greater number penetrate 

 those which have l>een more strongly narc >ti>ed. 



In all unfertili>ed f^irs the whole course of development becomes 

 iihnorinal. But whether, as claimed in FOL'S hypoth. -i-. the origin 

 of double and of multiple organisms is referable respectively to tin- 

 penetration of two and many spermatozoa, must still be regarded as 

 loubtful. Certainly the question suggested richly deserves to be still 

 more thoroughly tested experimentally. 



HISTORY. The facts here given concerning the theory of fecundation are 



acquisitions of very recent times. To omit the older hypotheses, it was 



ally a-Mimed up to the year 1*7.1 that the spermatozoa pi-m-irati- in great 



numbers into the .-ubManco of the egg, but that they there lo- -.ivity 



and become dissolved in the yolk. 



I succeeded in my study of the eggs of Toxopneustes lividus in finding 

 an object in which all the internal phenomena of fertilisation ma. 



uined with ease and certainty, and in establishing (1) that inconsequence 

 of fertilisation the head of a spermatic filament surrounded by a >t.-ll:itr figure 

 makes its appearance in the cortex of the yolk, and is metamorphosed into a 

 small corpuscle, which I called spermatic nucleus : (2) that within ten m: 



icleus and spermatic nucleus copulate; (.".) that normally fertilisation i^ 



:::plisl:cd by only a altn/lf spermatic filament, whereas in patholoirieallv 



altei'i '-ral >permatn/.oa may penetrate. I \\a> i li'leatthat 



time to announce the proposition, that fertilisation depends upon the fusion of 



ually differentiated cell-nuclei. 



A te\\- in- nths later, VAN I ' i-: NK i > K N aniioiin'-e*! that in the case of Mammals 

 the seuiiieiitation-iuieleus arises from the fusion of two nuclei, as had 

 previously been observed by Ari:i;i:Acii and I'i iscin.i inti.e ,-ase of numerous 

 i -t her objects, and expressed the conjecture that <>ne of them, which 1 

 first a peripheral position, mi^ht in part resi;lt from the MibMa 



.1, \\hich, in preat numbers, as he maintained, fu>e and be 

 commingled with the cortical portion of the yolk. An a ; 



this made by Fol., who investiirated with the gre .,;! the eggs of 



Kchinoderm> at the very moment of the penetration of a spermatic filament 

 into the eirir. and di-oneivd th.- !'..ri'.atiiin of a o "raction. S 



then it has been e>tal>lishe<l l>y means of numerous researches (those of 



\KA, KOI.. HI:I:TWK;, CAI I;I:KI.A. K rrrn:i:. Nrssi:.\r\i. VAN 

 EBKKTII, FLKNIMIN-;, ZACHAUIAS. r.ovi:i:i. I'I.ATNKI:, I'MAN:, II-IIM, and 



