426 A. J. NICHOLSON 
cases have I found references to branched nuclei in cells which 
are not obviously secretory in function, but both of these con- 
cern embryonal structures which are undergoing rapid growth 
and are therefore in a state of great activity. Korschelt (18) 
cites cases of branched segmentation nuclei, and Seeliger (25) 
describes the branching of the nuclei in the muscle-bands of 
young Oikopleura. In the latter case the branching 
reaches an extraordinary high state of development, becoming 
finally a complicated reticular network of very fine threads. 
Korschelt (18) regards the formation of nuclear branches as 
a method of increasing the surface of the nuclei to aid secretion. 
Thus, speaking of egg-cells, he remarks, ‘Die Bildung der 
Fortsiitze stellt eine Oberflichenvergrésserung des Kernes 
dar, verméege welcher dessen Berihrungsfliiche mit der 
Zellsubstanz erheblich vergréssert wird. In aihnlicher 
Weise wurde die Bildung von lingeren oder 
kiirzeren Fortsitzen des Kernes bei secerniren- 
den Zellen verschiedener Art beobachtet. Hier 
waren die Fortsitze nach demjenigen Theil der 
Zelle gerichtet, wo die Secretion stattfand.’ 
Tt will thus be seen that the form and position of the nucleus 
of the oocyte in A. maculipennis indicates that it is 
secretory in function and comparable to the nuclei of secreting 
cells. This similarity is further shown by the fact that during 
the process of branching the nuclear contents break down and 
form a granular mass, a process which normally takes place 
in secreting cells during the period of activity. The close rela- 
tion of one end of the branching nucleus to the nurse-cells and 
the other to the area of maximum activity of the growing 
oocyte, i.e. the posterior end, together with the relatively 
deeply-staining mass of cytoplasm between the nucleus and the 
nurse-cells, renders it difficult to imagine that the branching 
nucleus can be other than secretory in function. It is from the 
somewhat similar arrangement in other cells that Korschelt (18) 
draws the conclusion that the nucleus takes an active part in 
the nutrition of a cell. Thus he observes, ‘ Das Aussenden von 
Fortsiitzen und Anniherung des Kernes an diejenige Seite der 
