308 Thos, H. Montgomery. 



cations of the former process (note the position of the mitotic spindle 

 at the left edge of Fig. 31). This process results in a heightening of 

 the margins of the germ disc, which is well exhibited on alcoholic 

 surface views (Figs. 29, PI. II; 33, PI. Ill; 44, PI. IV). The vitel- 

 locytes produced thereby do not differ in appearance from the others. 

 Branched vitellocytes rarely show signs of division, and it is probable 

 that those which have become large and ramified do not divide ; they 

 do not wander beneath the extraembryonic blastoderm. 



The germ disc has not increased perceptibly in extent, but has 

 become sharply delimited from the extraembryonic area (Fig. 34, 

 PI. III). Its cells are closely apposed and have lost their intercellu- 

 lar branches. In the extraembryonic region the blastoderm still con- 

 sists of membraneless branched cells. 



4. 8tage of the Protozonites. 



This stage is evidently of short duration, for I found it in only two 

 lots of eggs, of the age of 60 hours. Fig. 45, PI. IV, exhibits the 

 earliest condition seen, one with four rather indistinct protozonites, 

 and Figs. 46 and 47 (lateral and ventral views, respectively) with 

 five protozonites. The germ disc has changed from a circular to an 

 ovoid outline, with one end broader than the other; the broader end 

 marks the beginning of the cephalic lobe, and the narrower, the 

 caudal. There are no longer projecting cumuli, but on median sec- 

 tion the caudal end {Gaud., Fig. 48) is seen to correspond in position 

 with the earlier posterior cumulus by the continuance of the group 

 of large vitellocytes at that point ( Vit. C. ) . The five protozonites of 

 Figs. 46 and 47 appear on stained whole mounts darker than the 

 intermediate regions because they are thicker, show no signs of appen- 

 dages and represent the beginnings of the segments of the pedipalps 

 and the four pairs of legs, while the protozonites of Fig. 45 represent 

 the segments of the pedipalps and the three anterior pairs of legs. 

 The boundary between cephalothorax and abdomen is that point 

 where the ectoblastic cells are somewhat flattened (Th. Ah., Figs. 48, 

 50b) ; previously this region had lain just anterior to the posterior 

 cumulus (Figs. 41a, PI. Ill; 42a, PI. IV). On comparison of Fig. 

 41a with Fig. 48 it follows that the elongation of the germ disc pro- 



