iiA'JTi; uit..\ Of TIII-: 



AM. PBOCBM 39 



are in tin- r->jMM-t in > ' ion. ( 'mis 



ntly it was by means of them tluU an ac'-m-ate in-ii:ht int<> th- 



rtili.vition \va> tii'M M rim-d. Tlr-y may tli.-n I'm-*- 

 in the following account as tin- foundation ( .t' our dex-ript ion. 



It' ripe rggs with ogg nucleus we n-mov. d from tin- ovary mi 

 watch ^las. containing sea-water, and a small (juantity of >eminal 

 fluid is added, a very uniform n suit is ol.taine.l. >ince in tin* comx- 

 <>f live ininuti-- 'lie of many hundn ds >r tluus:md> 



nornrilly frriilis-'d. as fan h<> acrurat ly uli- -rvi d l>y mean- of hi^li 



magnification. 



. \lthouirh spermatozoa attach themselves tothegelatinoufl 





Fig. 18. Fig. 10. 



Fig. 18. Fertilised egg of a Sea-urchin. 



The head of the sj>ei ui.it'>/.,i m whieh ]>enetrated haa lieen converted into a spemi-nucleut (*t) 



;iilel by ;i protoplasmic radiation, and has approached the egg-nucleus (ek). 

 Fig. 13. Fertilised egg of a Sea-urchin. 



' .4-) and the egg-nucleus (ek) have come close to each other, and both arc 

 surrounded by a protoplasmic radiation. 



of an egg in groat numbers, many thousands of tin in whon con- 

 ri ntratrd seminal fluid is employed, still only a single one of thorn 

 is concerned in fertilisation, and that is the one which by tin- lash- 

 like motion of its filament first approached the egg. Wln-n- it strikes 

 tin- surfac,' of tin- i-gg with the point of its h ad the clear MI]>: rtirial 

 rxpan>r of the egg-protoplasm is at once elevated into u small knob 

 that is ofti'ii drawn out to a fine point, tin- so-i-alh-d nv j.iivi- promin- 

 i>t'iiii<jii is.i/ti'ii/el), or cone of attraction. At thi> placo tin- 

 M ininal lilament, with pendulous motions of its caudal app.-ndage, 



bores its way into the egg (fig. 17 yl, /?). At tlu- >am- time a tin.- 



lui-inbraiu- (lig. 71 (' detach, s itself from tho yolk ovi-r tin- whole 

 surface, beginning at the cone, and becomes >eparat-d irom it by 

 an rvrr-im-ivaMiig Bpaoe. The spac.- probably arises beeaiiae, in 

 consequence of fertilisation, the rg_ - and presses 



