394 
CHIXOMATSU ISHIKAWA. 
such as chromic, picro-sulphuric, or nitric. They appear dis- 
tinctly as white bands on the now orange-red (with chromic) 
or reddish-yellow (with picro-sulphuric or nitric) portion. They 
represent the formative place of the eggs, and are filled with 
young ova that have not yet acquii’ed yolk- elements. I desig- 
nate these bands under the name of “ germogen ” inasmuch 
as it is in these parts that the primordial ova are found. The 
rest of the ovary will be spoken of as “ vitellogen,” where the 
vitellus or the yolk-elements are formed. 
A section of an ovary (fig. 3) will therefore show two 
distinct groups of eggs, one consisting of larger and the other 
of smaller eggs. The former (fig. 3, Vit.) fills up nearly the 
whole cavity of the ovarian sac, while the latter (fig. 3, ger.) 
occupies only a small portion. This latter represents the 
white band shown on a surface view (fig. 2 , ger.). 
The section represented by the fig. 3 is a transverse one cut 
through the posterior portion of the ovary, the smaller group 
of eggs occupying the outer side of the tube, and the larger 
the inner. 
This arrangement seems to be almost universal in the crus- 
tacean ovary. The sexual organs of Amphipods have been 
studied by Bruzelius, Spence Bate, and de la Yalette St. 
George. They have all described these organs as cylindrical 
tubes, whose peripheral parts are occupied by young eggs, while 
the central portions are filled with much more advanced eggs. 
Of the Isopod ovary Leuckart says : “ The ripened eggs always 
take the whole inner side of the egg sac; the youngest, on the 
contrary, lie on the outer side in its entire length. Only the 
outer side is the formative place of the eggs.” Edouard van 
Beneden, in speaking of the Amphipods and Isopods together, 
expresses his views in the following words (^-f -^) : — “ In all 
these animals there must be distinguished throughout the 
length of the ovary two very distinct parts ; the one situated 
on the external side presents itself under the form of a narrow 
band, and filled with young eggs at different stages of 
development.” 
The Ostracod ovary is stated to be of a similar nature (^). 
