1905.] NATURAL SCIENCES OF PHILADELPHIA. 185 



sekundaren Keimblaschen einander opponierten Vierergmppen ange- 

 horen. Es muss sich also schon die dicentrische Wanderung in einer 

 ganz gesetzmassigen, Quadrillenahnlichen Ordnung vollziehen, mdgen 

 dabei regulierende, von den Chromatinelementen selbst ausgehende 

 Reize oder irgend welchc als Leitbahnen dienenden Kernstrukturen 

 eine Rolle spielen. Bei der Paarung der Spalthalften erfolgt die 

 Vereinigung je einer vaterlichen und einer miitterlichen Spalthalfte. 

 Von den beiden einander opponierten Vierergmppen ^ und -^ werden 

 sich z. B. jeweils zwei Spalthalften ab und no miteinander verbinden 

 und das Gesamtresultat des sersten Teilungschrittes ist demnach eine 

 gleichmassige Durchmischung der vaterlichen und miitterlichen Anteile 

 (Textfig. Cb unten)." This recalls Fol's (1891) quadrille of the centro- 

 somes! The result of it all amounts to this: spermatid and ovotid 

 have each six bivalent chromosomes, the fertilized egg has twelve 

 bivalent chromosomes, and the same number is found in the first polar 

 spindle where they are arranged in two planes; each second ovocyte 

 receives twelve bivalent chromosomes, and there unite into six quadri- 

 valent chromosomes; and these undergo a reduction division in the 

 second mitosis, so that the ovocyte receives six that are bivalent. 

 This analysis is so intricate and complex, so little borne out by the frag- 

 mentary and somewhat doubtful evidence — only certain lines travers- 

 ing a nucleus — that we can charitably say thepaper is its own strongest 

 critic. It is to be much regretted that Hacker has used these results 

 in a general review (1904) of bastardization, because they are irrecon- 

 cilable with all other work, and tend to make the supposed diversity 

 and contradictoriness of the germ cell phenomena even more marked 

 than ever before. We are not in any need of "Referate/' but very 

 pressing need of more observations. 



The work of Linville (1900) on Limncca is not conclusive, for the 

 chromosomes are very minute and the prophases were not studied at 

 all; the same may be said of Francotte's (1898) study of Polyclades, 

 where the only figures are indistinct microphotographs. The investi- 

 gations of Van der Stricht (1898) and von Khnckowstrom (1897) upon 

 Polyclades have been strongly contradicted by Schockaert (1902), 

 who has given a much more detailed examination than either of these 

 writers. The papers of Prowazck (1901, 1902) I have not seen. Miss 

 Wallace's paper (1900) is admittedly indecisive, and Griffin's (1899) 

 studies on Thalassema and Zirphcea concern chromosomes of very intri- 

 cate forms and small size, and their behavior was elucidated (or should 

 we say nigrificd?) by an analysis of their final shapes. So none of these 

 investigations are decisive in any manner that requires rigid proof from 

 a study of the whole series of changes. 



