54 MARUUS M. HARTOG. 
Though we are now considering gametogeny, we must turn 
aside to note that in most cases of so-called ‘ parthenogenesis ” 
of Metazoa only one polar body is formed, and the ovum, 
rather a progamete than an oosphere, segments and develops 
directly. We revert to this process below in its proper 
place (p. 74). 
We must, however, note that in some cases the true oosphere, 
differentiated by two mitoses (i. e. the formation of both polar 
bodies), is a facultative gamete, and may develop without 
fertilisation ; this has been demonstrated in Liparis dispar 
and some other Lepidoptera, and in the Hive Bee (Apis 
mellifica) ; and in the last case the produce of the unferti- 
lised oosphere is always a male or drone. This is proof con- 
clusive that the formation of polar bodies is not necessarily an 
elimination of male elements or “ katastates ;” on the other 
hand, it would work in well with the very old view that in 
bisexual union the “ superiority” of one parent determines 
that the offspring shall be of the opposite sex. But such 
considerations are outside the limits of our theme. 
VI. A GENERAL VIEW oF GAMETOGENY. 
Before summarising the results of our systematic survey 
we have to consider several points of general bearing. 
A. The Reduction of the Chromatomeres in 
Gametonuclei.! 
A frequent, but certainly not universal, process in gameto- 
geny is the reduction of the number of chromatomeres or 
these eggs, destined to form the two polar bodies and to be fertilised by a 
spermatozoon, a portion of the nucleus is segmented off before maturity 
and remains in the egg, ultimately to fuse with one of the segmentation 
nuclei at the first or third segmentation. I confess myself unable to explain 
this fact, or bring it into line with other phenomena of gametogeny. 
1 Most of the details of this section are taken from Strasbiirger, ‘ Kern- 
und Zelltheilung ’ (1888), and from R. Hertwig’s paper cited above ; and dur- 
ing the impression of this paper I have consulted Guignard’s ‘Sur la Consti- 
