1908.1 PHILLIPS—A REVIEW OF PARTHENOGENESIS. 809 
persist despite the fact that the mass and, as far as we can see, the 
quality of the chromatin is the same in both cases.’’ 
Blochmann (1889) studied the maturation of drone and worker 
eggs in Afis meliifica with the following results: The first polar 
nucleus is given off normally and remains undivided, but the second 
polar nucleus often appears to divide. The fact that these three 
nuclei are not, as in some cases, due to a division of the first polar 
nucleus is proven by the position of this nucleus, which is always 
found just under the surface of the egg and separated by some dis- 
tance from the other two. The female pro-nucleus soon becomes 
vesicular in form and goes to the axis of the egg, where it forms 9 
spindle and gives rise to the blastoderm cells. The polar nuclei 
change as in Musca vomitoria, but do not become vesicular in 
form, approach one another and are enclosed by a rather large 
vacuole of the superficial protoplasm, which is free from yolk. In 
this vacuole they break up into fine chromatin granules, which 
become. scattered through the whole cavity of the vacuole. We 
may suppose that the contents are later removed from the egg. In 
fertilized eggs the ovarian nucleus undergoes the same divisions as 
the unfertilized. 
Platner (1887) also found two polar nuclei in Lzfaris dispar, a 
parthenogenetic Lepidoptera. These two cases, the first two 
recorded, are not in accord with the previous views of Weis- 
mann, and in 1891 he sought to explain these cases as follows: 
** Das Kernplasma einzelner Eier einer Art das Vermégen des Wachs- 
thums in grésserern Masse als du Majoritat derselben besitze, oder, 
im Falle der Biene, jedes Ei besitze de Fahigeit, sein auf die Halfte 
reducirtes Kernplasma, wenn es nicht durch Befruchtung wieder 
auf das Normalmass gebracht wird, durch Wachsthum wieder auf 
die doppelte Masse zu bringen.’’ 
Petrunkewitsch (1901), studying Afzs, found that eggs laid by 
the queen in drone cells never showed any signs of having been 
fertilized. As in a fertilized ovum the first polar nucleus is separa- 
ted by an equatorial division, in the second maturation there is a 
reduction of chromosomes to one-half. Similarly the first polar 
nucleus always divides with a reduction and the peripheral half is 
liberated and perishes. The restoration of the number of chro- 
mosomes in non-fertilized eggs probably occurs by a longitudinal 
splitting of the chromosomes, but with a suppression of the corre- 
sponding division into two daughter nuclei. The central half of 
