602 
ME. LUBBOCK ON THE OENEEATIVE OEOANS, AND 
of the young ovules, however, is by no means the same. They do indeed form two 
distinct series, as is the case in all Chilognaths ; but instead of eggs in all stages lying 
indiscriminately next to one another, and without the least arrangement, we here find 
all the youngest eggs occupying the inner border of the series ; and as we pass across 
the series from the median line of the body to the sides, we pass from the youngest to 
the oldest eggs. Moreover each line of eggs is in approximately the same stage of 
growth ; so that all the eggs in the outer row and all the inner row are respectively of 
nearly equal size, and those constituting the intermediate rows are of intermediate 
dimensions. The smallest eggs which I could see well were rather less than TWoth of 
an inch in diameter, and quite transparent. They did not seem to be enclosed in any 
distinct follicle, although in later stages, when they had increased to of i^oh 
in diameter, an epithelial membrane with distinct nuclei could be seen as distinctly as 
in lulus. In the very young eggs, however, I could never see a trace of it ; yet them 
margin was so clear and well marked, that it was difficult not to believe that each egg 
was formed by a true cell. Moreover, under the action of dilute spirits of wine the 
yelk darkened, and often contracted irregularly, in which case the margin of the egg 
remained as before, and was perfectly distinct. 
We have here almost the same difficulty as in the question about the skin of certain 
Infusoria ; but the point is perhaps of more importance, since if we regard each egg in 
Polydesmus as a specially modified cell, we could no longer consider it as homologous 
with the egg of certain other Myriapods, as, particularly, of Glomeris. I have, however, 
never met with any stage intermediate between the youngest eggs and the true epithe- 
hal cells, and cannot, therefore, at present solve the question. 
In very young eggs the Purkinjean vesicle scarcely seems to possess any definite 
membrane ; and sometimes, even in eggs as much as of an inch in diameter, 
on the addition of pure water its outline became flocculent, and finally disappeared. 
Different eggs, however, behave very differently in this respect. In Plate XVI. fig. 8, 
I have represented three eggs as they appeared at the same time in the field of view. 
They were dissected out in sugar and water, and then put into pure water. One {a) 
has remained unaltered, except that the macula has become, as usual, darker ; in the 
second [h) the Purkinjean vesicle has disappeared and the macula remains ; in the 
third (c) the macula has disappeared and the Purkinjean vesicle remains. 
I did not see in Polydesmus anything equivalent to the “ patch ” which occm's in the 
young eggs of lulus. In the smallest eggs the macula was already very distinct. In a 
few cases it seemed to contain one or more nucleoli, but generally it gave me the j 
impression of being a more or less solid body attached to the wall of the Purkinjean i 
vesicle. At first the Purkinjean vesicle was • 2 (foo'th or ^^-oth of an inch in diameter, I 
or about half as large as the egg ; when, however, the egg has increased to ^ioth, the j 
Purkinjean vesicle has only increased to about y^ooth. At this stage the yelk-granules ' 
commence to be formed in the egg ; they are at first very small, and give it a broAvnish | 
appearance. i 
