STUDIES OP REPRODUCTIVE ELEMENTS: I. 25 



mosomen liereits in der reduziei'teii Zah] zum \ orsdiein. Fnlls also 

 Weismanu seine theoretische postulierte Keduktion der Z-dd der Ahnen- 

 ])lîismen mit dieser thatsächlichen Iveduktion der Zahl der Chromos(j- 

 men identifizieren will — ^Yas rdcht nothwendig ist — so niuss er die 

 Annahme, dass dieselbe durch die l>ilduno- de.-! zweiten Hichtungsk()r- 

 j)ers vermittelt werde, aufgeben." 



But as the observations of Bovcri on this point in Ascaris were 

 proved not to hold true by the above cited investigation of Hertwig, 

 T will not treat of it again here, but will oidy refer the reader to his 

 I )ea utiful monograph. 



The latest series of ()l)servations come from Hacchcr'''^ arid Ileuh- 

 m^,'"'^"' botli of whom also admit the introduction of a re<luction of 

 chromatic elements at the Ijeoinnino' of each embrvou'enesis. Thev 

 admit, however, this to take place in the formation of the first polar 

 body and not in tliat of the second. Haechcr who studied the formation 

 of the polar bodies in Cijchps gives a couple of very fine woodcuts, which 

 lead one to think that the " Jieduktionstheilung " takes place in the 

 formation of the first polar body. xVs in the case of Diaptomus, the 

 chromosomes in the sexual cells of Ctidops number eight. These 

 divide longitudinally in stage A, and produce sixteen elements, every 

 two of which lie close together and thus form eight groups of double 

 elements. In stage ]>, they liecome se])arated into two groups each of 

 four double elements, one of which serves f(n' the formation of tlie 

 first polar body. The remaining four double elements now arrange 

 themselves to form the second polar spindle (stages C and D). Haeckcr, 

 however, quite rightly d(^es not regard his observations as to the 

 stages in which the " Reduktionstheilung " takes place as conclusive. 

 After discussing the possil:)ility of Booeri's discoveries in eggs of Timm., 

 Echinus, Garinaria, Pterotracliea, and Fhyllirrhoi being in accordance 

 with his own view, i.e., that the " Reduktionstheilung " takes place 



