68 MCMURRICH. [Vol. XI, 



ing from the dorsum to the oviducts along which they passed 

 had also disappeared in this stage, a fact which suggests the 

 origin of the canals as an in-pushing of the hypodermis in front 

 of the spermatophore. 



If this interpretation of the observed phenomena be correct, 

 we have an example among the Crustacea of a phenomenon 

 which resembles not a little that termed by Whitman ('91) 

 hypodermic impregnation, although the conveyance of the 

 sperm to the oviduct is somewhat more direct than in the typi- 

 cal cases he records. Examples of the phenomenon have been 

 found in various groups of Invertebrata, as will be seen from 

 Whitman's paper, but, so far as I know, nothing similar to 

 what occurs vsijaera has been recorded for other Crustacea. 

 Spermatophores occur in many forms, such as the Copepods, 

 Thysanopodous Schizopods, and some Decapods, and further- 

 more, copulation, during which the male rests on the dorsum 

 of the female, is very frequent, but I know of no previously 

 recorded case where the spermatophores are inserted upon the 

 dorsal surface of the body. 



2. The Formation of the Egg-Memhranes in Jaera. 



The newly-extruded tgg of Jaera is of a bright grass-green 

 color, similar to that which Rathke ('37) has described and fig- 

 ured for Bopyrus and Janira, and is somewhat irregular in 

 shape, later, however, becoming oval and measuring on the 

 average about 0.2 mm. in length by 0.19 mm. in breadth. In 

 the center of the o^g^ is the nucleus enclosed within a stellate 

 mass of protoplasm, a thin peripheral layer of this same mate- 

 rial enclosing the yolk spherules, which are mainly albuminous 

 with a few oil globules. Sections of about half-grown ovaria-n 

 eggs (PI. V, Fig. 2) show that a delicate network of protoplas- 

 mic fibrils {pn) extends from the central {cp) to the peripheral 

 protoplasm, the yolk granules lying in the meshes of the net- 

 work in the manner described by P. Mayer ('77) for Eupagn- 

 riis; in later stages and in the mature ^gg the network cannot 

 readily be made out, being obscured by the great development 

 of the yolk, but the peripheral protoplasm (Fig. 3, //) can 

 readily be seen during the early stages of segmentation. 



