﻿Contr. toward the Embryol. and Anat. of Pol. pallipes (Hymenopt.). 145 



follow each otlier is extremely difficult, and we can only give what 

 it seems to us, after studying all our sections, is the correct sequence. 

 Longitudinal sagittal sections would show which were the early and 

 which the late stages of development, but when we add to these 

 longitudinal sections, cut in other than a sagittal plane, and also 

 transverse sections, the task of selection becomes difficult. 



Following the two stages we have briefly described we find 

 another change taking place which is best seen in a transverse 

 section. Here (Fig. 46), we notice the first definite arrangement joi 

 the cells, in that, along one part of the section there is a grouping 

 of a number of columnar cells. These are found only at one place. 

 The cells covering the remainder of the section are flattened against 

 the egg. This arrangement is not shown in a section near either 

 end of the egg (Fig. 47), a longitudinal sagittal section of such an 

 egg, shows that the cylindrical cells are grouped along one surface, 

 beginning nearer one end than the other. We are now able to 

 determine that the surface bearing the cylindrical cells is ventral, 

 and that the end, nearest which they occur is anterior. This forma- 

 tion, part of the ventral surface of these cylindrical cells, we find 

 persists. To follow this would lead to a study of the germinal band 

 which is beyond the scope of this paper. 



The yolk nuclei, 



Eegarding the origin and fate of the nuclei which are found 

 within the egg after the blastoderrn is formed there has been much 

 dispute; at present no general statement can be made, if different 

 insects are considered. Concerning the ultimate fate of these nuclei 

 we here have nothing to say. Our observations have extended as 

 yet but a short time after the blastoderrn is formed, and, at this 

 stage, the nuclei are still present within the egg, being easily seen 

 in any of the pre-blastodermic stages we have described. We are, 

 however, at present interested in the yolk nuclei during the stages 

 we have herein recorded for Polistes, and will give their history 

 only so far. 



In regard to the origin of the yolk nuclei there are two distinct 

 views advanced; one accounts for their origin from the dividing 

 nuclei within the egg and follows in general what we have so far 

 described as occurring in Polistes; the other derives the yolk nuclei 

 from the cells of the blastoderrn, holding that their origin is in the 

 blastoderrn, and that they wander back into the egg. Mention might 



Zeitschrift f. wissensch. Zoologie. LXXX. Bd. 10 



