NO. 1783. NORTH AMERICAN LERNJ^OPODID.^L:— WILSON. 217 



judging, as he admits, entirely from external appearances. The nature 

 of this plug is clearly proved by the way in which it stains. It is not 

 the peg, for that remains uncolored in both hsematoxylin and eosin; 

 it is not part of the gland itself, for that takes a deep-blue stain; it 

 is the secretion of the gland, which stains deeply with eosin. The 

 very rudimentary eye, which was found in the nauplius-metanauplius 

 stage within the coils of the attachment filament, has entirely disap- 

 peared. It goes without saying that there can be no remnant of the 

 lenses left, for there were no lenses to begin with in this species. 

 Moreover, there was no pigment in the larval eye, and hence the 

 irregular pigment spots found on the dorsal surface of this larva, above 

 the brain, can not be explained as ''taking their origin in the pigment 

 of the larval eye," which is the explanation given by Claus for 

 Achtheres percarum. 



EXCRETORY GLANDS. 



In addition to these frontal glands, there are several excretory 

 glands in the head, some of which are more or less connected with one 

 another. The largest starts at three different centers on the level of 

 the bases of the maxillipeds. One center is median and dorsal, be- 

 tween the wall of the anterior end of the stomach and the dorsal body 

 wall (mjjg., fig. 32). This may be designated as the median center of 

 the maxillipedal gland. It begins as two or three ellipsoidal balls or 

 accretions of very small cells, gathered just beneath the ectoderm in 

 this region of the back. These are supported by a fine meshwork of 

 connective tissue from the dorsal ectoderm, the outside layer of the 

 stomach wall, and the adjacent dorso-ventral muscles, wliich operate 

 the second maxillae and the maxillipeds (fig. 37). 



At first these glandular masses are small and, especially in the 

 female, are often spherical; but as they increase in size they accom- 

 modate themselves in both sexes to the shape of the cavity in which 

 they are formed. Elongating antero-posteriorly, they become ellip- 

 soidal or cylindrical and often taper into cones (mc, fig. 37). Owing 

 to the position of the ovaries or testes close behind them on the 

 median line, these masses move around to the sides of the stomach as 

 they increase. Here they grow backward until they overlap consid- 

 erably the anterior end of the sex organs. Sometimes this lateral 

 movement eventually draws the masses away from the midline, leav- 

 ing that space free for the maturing ovaries and testes. 



As soon as this median portion of the gland appears, a similar mass 

 may be found on either side near the bases of the maxillipeds (Ic, 

 fig. 32). These lateral maxillipedal centers increase similarly to the 

 median one, and finally fuse with it around the sides of the stomach. 

 A spirally convoluted duct (d, fig. 37) is then formed, leading from 

 the fused lateral mass on either side to the base of the maxilliped, 



