BIOLOGY OF PARACOPIDOSOMOPSIS. 43 



of spherical granules arise at its periphery, giving it the appear- 

 ance of a lobulated structure (Fig. 4). Eventually the nucleolus 

 breaks up into a number of these large granules, which lie in a 

 finely granular matrix (Fig. 5). Apparently these larger granules 

 coalesce to form the chromosomes (Fig. 7). From a careful 

 study of this particular stage, one can not escape the conclusion 

 that the chromosomes arise from the nucleolus. 



A somewhat similar method of origin of chromosomes has 

 been described by Meves and Duesberg ('08) in the male germ 

 cells of Vespa crabro, They say: "Das Herannalien der ersten 

 Reifungsteilung macht sich dadurch bemerkbar, das im Kern in 

 der Umgebung des grosseren Nucleolus immer mehr Chromatin- 

 korner auftreten. Der Nukleolus selbst wird dabei immer 

 kleiner. Man gewinnt den Eindruck, dass seine Substanz in 

 diejenige der Chromatinkorner iibergeht." There is one impor- 

 tant difference between the two forms. In Paracopidosomopsis 

 the nucleolus gradually but completely disappears as the chromo- 

 somes are formed, while in Vespa a small body still remains 

 after the chromosomes are organized. 



During the organization of the chromosomes the nucleus 

 elongates in the direction of the long axis of the cell. An 

 imperfect intranuclear spindle then arises, and upon this the 

 chromosomes tend to take up an equatorial position (Figs. 6, 8). 

 They are usually so closely massed together that it is impossible 

 to make an exact determination of their number. Fig. 6 shows 

 a very interesting case, in w r hich a single curved chromosome 

 has moved to the upper end of the nucleus, where it lies in con- 

 tact with the inner surface of the nuclear membrane. On 

 account of the massed condition of the chromosomes, it is not 

 possible to tell whether this particular chromosome is the product 

 of a recent division, and has a sister chromosome lying within 

 the mass. However, this is an isolated case, and it is clear that 

 the chromosomes do not normally divide in the first spermatocyte 

 division. Instead, only the cytoplasm undergoes division, and 

 this in a very adequal manner (Figs. 7, 8). 



The constriction of the cytoplasm begins about one-third the 

 distance from the pointed end of the cell (Fig. 7) and finally 

 results in cutting off a small, knob-like mass entirely free of 



