The Spermatogenesis iu Pentatoma up to the Formation of the Spermatid. 79 



B. The chromosomes appear in the normal number in 

 the 1st spermatocytes (or ovocytes). 

 1) 1 ehraination division, followed by transverse (?) or longi- 

 tudinal (?) division Ophryotrodia 

 V 2) 1 elimination, 1 longitudinal division Fyrrhocoris 



3) 1 elimination, 1 transverse division (what is their sequence?) 



Gdloptenus 



4) 1 division, 1 elimination Lumhricus 



A chromosome, as we have defined it, is a particular, separate 

 chromatin element: its prospective or retrospective value should not 

 be considered as modifying its definition as a special morphological 

 unit; the valence is something different from the actual value. 

 In determining the valences of the chromosomes of the reduction 

 divisions, we must again start with the chromosomes of the adult 

 tissue cells, the spermatogonia and ovogonia, which are granted generally 

 to be univalent. The spermatid and ovum cannot be taken as the 

 starting point, since it is in them that we have to determine the 

 valence of the chromatin elements. The chromosomes of the 1st re- 

 duction division are univalent, when they occur in the normal number; 

 bivalent, when they appear in half the normal number. If a case 

 should be demonstrated where chromosomes appear in double the normal 

 number in the 1st reduction division, such chromosomes would neces- 

 sarily be semivalent. Applying these deductions to a particular case, 

 e. g, Fentatoma, we find the following valences for the different gene- 

 rations of cells: 



Spermatogouium 14 univalent chromosomes 

 1st spermatocyte 7 bivalent „ 



2nd spermatocyte 7 univalent „ 



spermatid 7 semivalent „ 



Or in Calopienus (my interpretation of the elements): 



Spermatogonium 12 univalent chromosomes 



1st sjDermatocyte 12 „ „ 



2nd spermatocyte 6 „ „ 



spermatid G semivalent „ 



or : 

 1st spermatocyte 12 univalent chromosomes 



2nd spei-matocyte 12 semivalent „ 



spermatid 6 „ „ 



Or iu Ophrijotrocha: 



Ovogonium 4 univalent chromosomes 



1st ovocyte 4 „ „ 



