194 
Katharine Foot and E. C. Strobell 
wird sich somit die Kraft aller Eizellen konzentrieren, die mit dem freien 
Raum verbunden sind. Diese Kraft aber äußert sieh durch die Zer- 
setzung der umliegenden großen Kerne« p. 614. 
Tliis plasma space which has been called a “canal” or “duct” by 
earlier writers, can be clearly demonstrated in Protenor and it can be 
shown that in mature ovaries it is in direct Connection with the young 
eggs (fig. 1, plate XII). 
Earlier writers observed this “canal” in the ovaries of many insects 
and interpreted it as a means of conveying nutritive substance, “velk 
matter” to the growing egg, this substance being secreted by the large 
cells of the terminal chamber. 
In 1859 Lubbock wrote, “Professor Huxley has observed in Aphis 
and I have noticed in certain Hemiptera that a tube or channel leads 
down from the terminal chamber into the second and third egg chambers, 
which seems evidently intended to convey velk-matter to the developing 
eggs”, p. 348. He tliinks there can be “no doubt that it is really a duct 
through which the yelk-substance*descends to the growing egg”. The 
cells of the terminal chamber which secrete the velk-substance have 
been called Vitelligenous cells and Stein, Huxley, Leuckart and Lub- 
bock all agree that they secrete the “yelk-matter” which is conveyed by 
the “canal” to the growing egg. 
Fig. 1 and pliotos 3 and 4 demonstrate that Protenor Supports the 
observations and conclusions of these earlier investigators. There are 
several features which seem to indicate that the large nuclei of zone B 
secrete a substance which is conveyed directly to the growing egg, through 
a canal-like space and this canal is later in direct Connection with the 
youngest egg chambers. We have found it most conspicuous in tliose 
ovarian tubes in which the young egg chambers are forming (fig. 1 and 
photo 3). In successive earlier stages its presence is less and less evident. 
In longitudinal sections of entire tubes of ovaries from young individuals, 
before the last moult, the egg chambers are still undeveloped though 
young germina! vesicles are to be found in zone C. 
In the immature ovaries in which a definite “canal” is not evident, 
delicate canal-like spaces are present in zone B, similar to tliose seen 
in the mature terminal chambers, and which in these later stages lead 
into the central canal. Such spaces are demonstrated in the mature 
terminal chambers of fig. 2 and photo 1, and adjacent sections of this 
terminal chamber sliow that these delicate canal-like spaces lead into a 
central “canal” fully as pronounced as the one shown in figure 1. Photo 3 
shows a part of one of the adjacent sections in which the “canal” is 
