lIATDBATlOa Of 'riir. KOO, AM. PROOM Of PEin i -11 



rved, either completely oral lea.-t partially, in numerous ol 



animals al>o in Co hi. 



< '\I;NI\ . X\< II AKIAS, hovKKi. l'i. \INKU). ami in Mollu-c- and V 



brate>. A- regard.- the 1 ist, it lias been possible to follow accur.-' 



in tlu case of Petromy/.on t'ie penet rat iun -t' 



into tin- egg through a ,-prcial preformed mieropyle in tin- vitelline 



membrane (< 'AU;KKI. A. K riMTKi:. UI:M:. K i:. and B6*Hlf), Like\\ 



tin- Anij.hiliia, proof ha> been brought forward that after !',- 



a >i n TIM -inn-It -us i> formed at the animal pole, and that, surround.-,! by 



a pigmented area, derive! from the coitex of the yolk, it nmv, 



\\;,rd anotl'.er more deeply imbedded nucleus (c,:^-nurleu>). and fnsefl 



Avith it (0. HKUTWK;, UAMISKKI:, BORN). In Mammals the tVrtilisa- 



tion takes place in the beginning of the oviduct. Evidence ha> a No 



heen produced in their case that after tin- liberation of the : 



tells two nuclei are temporarily to be seen in the egg-cells, and I 



unite in the centre of the egg to form the ch 

 (VAN I;I:M:M:\. TAT 



Thi> i- the proper place in which to mention briefly the so-callel 

 micropyle. In many animals (Arthropods, Fishes, etc.) the egg- 

 enclo>rd 1 -fore they are fertilised in a thick firm envelope, which 

 is impenetrable for spermatozoa. Now. in order to make fertili> 

 povMhh'. there are found in the>e casefl at a detinite place on the 

 membrane Sometimes one, sometime^ >e\eral. small openings (micro- 

 pyle>), at which the Bpermatozoa accumulate in order to glid' into 

 the interior of the egg. 



The egg of Nematodes has for several years rightly playe , 



:tant role in the literature of the process of fertilisation. But 

 this i> e>jn-i-ially true for the egg of the Maw-worm of the Horse 



iris inegalocephala). which VAN HKNKDKN has made the su 

 of a celebrated monograph. It is an excellent ubjtvt, in 80 tar 

 aa it not only can be h id for >tu ly everywhere and at all seasons of 

 fear, but al>o allow- one to follow -tt-p by step, in the most 

 accurate manner, the penetration and subsequent fate of the sper- 

 mato/oon. Since, moreover, the proce of fertili> it ion in A- 



,'licephala pre>ent> many peculiarit ie> in it- d- nde 1 



presentation of them is lx)th warranted and de>irable. 



Intheca-eof this\Voi m.in which the.-e.\e> are >ep. irate individ 

 there i> a coj ulation. and the fei t ili-atioii of thecjg tak-> place within 

 the R-xual paages of the female. In one region, which i> expanded 

 into a kind of uterus, mature >permatir Imdu-s are m.-t with in g 

 niniibers. The aj>pearance of these differ- greatly from that \\ 



