4 < o.Ml'ARATIYK ANATn.MY. 



The head of tin- sjcrniat<i/.iMiu, .>n fiilcrin;_' the ovum, is trails!.. nii.-.l int.. llir 

 male pronucleua, 1 which fusi-s with the IVinale pn.nii.-lcn- to form tin- first 

 segmentation nucleus. 



Impregnation then consists in a material fusion of tin- 

 generative products of both sexes, and hence in the new 

 individual we naturally find inherited qualities. The essential 

 cause of inheritance consists in the molecular structure of the 

 nuclei of both male and female germinal cells. This structure 

 (idioplasm) is the morphological expression of the characters of 

 the species and individual. 



-/J/v 



C I) 



Fid. 2. DlAul: \MS OK THK SKfi.MKM A I I' i.\ OF THE Ovi.M. 



A, first stage (two segments) : A'A', ]>..lar hr.di.'s. ]?, second stage (four si-gnn-nt.-. . 



('. Further stage. D, morula stage. 



The next stages (Fig. '2) are as follows. The first segmentation 

 nucleus divides into two equal parts, each of which forms a new 

 centre for the division of the ovum int.. t \\ .. halves. This division. 

 the beginning of the process of segmentation, takes place- 1>\- 

 the formation of a furrow round the egg, which becom..* deeper 

 and deeper, until the division is complete. 



The first stage in the process of segmentation is thus completed : 

 the second takes place in e\;K tly the same way, and results in a 



It til.' .-;- is In I..- Ii.irin:ill\ .li'Vclnjii'd. lint 



.T. Tho latter may either pass through a di-tinitc 

 its way through the viti-Hin.. m. mluHin-. 



tliaii nil.' sjM'rniiltn/noli must 



(mirropylf), or else 



