waite: antennal glands in iiomarus americanus. 183 



of tliirteen sections 10 micra thick through the left antennal gland of 

 the first larva. The sections are cut parallel to the long axis of the 

 antenna and perpendicular to the frontal plane of the larva, and are 

 viewed from the lateral face, Figure 32 being the most lateral one 

 shown. The members of the series reproduced do not extend near 

 enough to the median plane to include the opening of the duct to the 

 exterior, but the relations of this duct to the ectodermic sac and to the 

 external orifice may be inferred from Figure 38.. 



The ectodermic sac — the walls of which are represented in a lighter 

 shade than those of the endsac — is oval in shape, flattened vcntrally, 

 and elongated in the axis of the antenna (Figures 32 to 38, sac. ee'drm.). 

 The endsac (Figures 33 to 35, sac. trm.) lies in a depression of the ven- 

 trolateral face of the ectodermic sac, as is readily to be understood from 

 its position in the sections and in the series as a whole. The three 

 evaginations of the ectodermic sac — proximal, ventral, and dorsal — 

 are still indicated, though less prominently than in the embryo. The 

 passage from the lumen of the endsac to that of the ectodermic sac — 

 partly closed by the valvular Hap — is shown in Figure 33. 



The endsac (Figures 33, 34, sac. trm.) now lies closely applied to the 

 ventral wall of the ectodermic sac, a relation which is changed in later 

 stages (see p. 190). A ventral recess of the ectodermic sac shown in 

 Figures 37 and 38 leads distad and mediad to the duct communicating 

 with the external world. This is better shown in Figure 39, a section 

 of the left gland from another series, but viewed from the median face. 

 This being cut in a more favorable plane, at a slight angle with the long 

 axis of the appendage, shows that the ventral recess continues as a duct 

 to the external opening (of. ex.) at the summit of a papilla on the ven- 

 tral wall of the appendage. It is clear from this figure that the duct is 

 connected with the ventral face of the ectodermic sac. The position of 

 the duct marks the original course of the ectodermic ingrowth in the 

 embryo. 



The conclusions reached by the examination of such parasagittal 

 sections are supplemented by the examination of transverse sections. 

 Figure 40 (Plate 5) is the anterior face of a transverse section through 

 the first larva in the region of the base of the second antennse, and 

 shows the general position of the antennal glands, which lie almost 

 wholly within the appendage. Figures 41 to 48 (Plate 5) exhibit the 

 anterior faces of the third, fifth, seventh, ninth, tenth, twelfth, four- 

 teenth, and seventeenth sections of a series through the right gland, 

 Figure 41 being the most anterior. The sections, each 10 micra thick, 



