234 BUMPUS. [Vol. V. 



dermhiigel " of Reichenbach. In Crangon, at this stage, the 

 blastopore is closed. 



Suggestive is the line of nuclei extending posteriorly from 

 the blastopore (PL XV, Fig. 4), a feature not mentioned by 

 Reichenbach nor by Kingsley. 



A median longitudinal section at this stage (PI. XV, Fig. 7) 

 shows more clearly the exact amount of invagination at the 

 blastopore. Immediately posterior to it, in many specimens a 

 second shallow depression is to be noticed, which may be com- 

 parable with the "oval depression" of AtyepJiira. The ecto- 

 dermal cells will be found to be more crowded, smaller, and 

 deeper in the region of the procephalic lobes {Pel.). Extend- 

 ing into the yolk from the depression of the blastopore are 

 the rapidly proliferating elements of the entoderm, a mass of 

 large thin-walled cells with deeply colored nuclei. They are 

 apparently digesting the yolk (PL XV, Fig. 7, Ent.). These 

 entodermal cells, which are directly comparable with those 

 found in Atyephira, Astacus, and Crangon, have evidently been 

 proliferated from the ectoderm, though actual karyokinetic 

 figures were not observed. Extending out into the yolk from 

 the entodermal mass are pseudopodia-like prolongations, which 

 worm their way between the masses of food yolk. 



The chromatin nebulae are, as surface views showed, abundant 

 under the U-shaped embryonic tract ; and a few are seen deeper 

 in the yolk, around the entodermal mass (C.n). A few from 

 the anterior portion of the egg are highly magnified (x 1400) 

 (PL XV, Fig. 1). They rest between the masses of food yolk, 

 and range in size and structure from the smallest homogeneous 

 dot to bodies almost equalling the ectodermal nuclei in size, and 

 containing one or more deeply colored masses which I have called 

 nucleoli. 



The food yolk is often broken up into polygonal masses, prob- 

 ably the result in part of the action of reagents, and is punctured 

 with circular openings, the site of now dissolved oil globules. 

 A distinct line separating yolk from ectoderm cannot be drawn, 

 the ectodermal cells (Ect.) actually grasping the yolk granules. 

 The entoderm is not free from yolk. The cells, indeed, seem 

 to form a reticulum that holds a quantity of yolk grains in its 

 meshes. 



A transverse section through the blastopore (PL XV, Fig. 5) 



