296 Annals Entomological Society of America [Vol. XI, 



Pyloric valve. There is no pyloric valve. 



Imaginal ring. The cells at the extreme anterior end of 

 the hind-intestine are very small, narrow, and pressed closely 

 together; they probably constitute the imaginal ring of the 

 hind-intestine, although they never present a several layered 

 appearance. This is much the same condition which Poyarkoff 

 (1910) described for Galeriicella. 



Basement membrane. The basement membrane of one region 

 is continuous with that of the other. 



Circular muscles. The connective tissue sheet, in which 

 the circular muscle fibres lie, is continuous from the mid- 

 intestine into the hind-intestine, so that the circular muscles 

 of the two regions appear to be homologous and continuous 

 but doubtless embryological researches would show that, as 

 is the case with insects generally, they have entirely different 

 origins. There is a sphincter at the point of junction. 



Lofigitudinal muscles. The longitudinal muscle fibres are 

 continuous from the mid-intestine into the hind-intestine. 

 As the transition area is neared, the numerous longitudinal 

 muscles of the mid-intestine (fifty or sixty in number) come 

 together so as to form eighteen or twent}^ larger fibres, which 

 again penetrate through the connective tissue sheath of the 

 circular muscles, so as to lie outside of them, as is the case in 

 the fore-intestine. 



This condition is illustrated in figure 15. 



THE EVAGINATION OF THE SECOND SERIE.S OF MALPK.HIAN 



VESSELS. 



(It seems illogical to speak of the more anterior set of Malpigliian tubes as 

 the second series, but the writer prefers this usage, because he believes tliat the 

 close association of this series with the mid-intestinal epithelium is entirely 

 secondary, and that the opening of the bladder formed by the vessels of the first 

 series represents more nearly the primitive insertion of the tubes). 



The two Malpighian vessels of the second series arise at the 

 extreme posterior end of the ventriculus, appearing abruptly, 

 before there is any change in the mid-intestinal epitheliimi. 

 Their cells are, however, very distinct from the ventricular 

 epithelium. They are lined by a very faint striated border. 

 The lumen of the vessels is continuous with that of the intestine. 

 The tw^o vessels arise very close together. As soon as they 

 penetrate the connective tissue layer in which the muscles are 



