637 



In B. pentado7ita the jaw is about twice as wide as long, as in 

 B. astaci; but the large median denticle, gives it a pentagonal form. 

 The larger specimens measured as follows : 



Length at rest 3mm, in extension 4.5 mm 



Width of the first cephalic segment 0.2 



- - - second ~ - 0.3 - 

 - - first somite 0.225 - 



- - - seventh (widest) somite 0.45 - Lower jaw of 



B.pentadonta 



Length of the head 0.4 



This species is readily distinguished from B. astaci^ with which 

 it agrees nearly in size, by the form and structure of its head and by 

 the form of its body. In B. astaci the head is composed of four seg- 

 ments, while in B. pentadonta there are only two cephalic segments, 

 one small anterior segment and a large posterior one. In B. penta- 

 clonta the body is much wider near the middle than at the ends ; but 

 in B. astaci the width is very even. Short stout hairs may be seen 

 along the entire margin of the body in the new species, and these are 

 larger and more numerous along the edges of the lips. The lips are 

 entire, and, as in other species, the upper lip is plainly longer than 

 the lower. The oral papillae are comparatively long and slender and 

 14 — 16 in number. The receptaculum seminis is pyriform as in B. 

 parasita, and the species is thus easily distinguished from B. astaci in 

 which the receptaculum is cylindrical. That B. pentadonta is not a 

 young stage qìB. parasita is perfectly certain. The penis of -B. para- 

 sita is armed with small hooks at the end and has a bulbous enlarge- 

 ment at the base; in B. pentadonta the penis is perfectly straight and 

 smooth, showing no trace of hooks or of a bulbous enlargement. Then 

 the jaws are quite different in form and in the number of denticles. 

 B. pentadonta is found, so far as I have observed, chiefly on the an- 

 terior pair of ambulatory limbs, on the inner side of the first long joint. 

 B. parasita is found on the eye-stalks, the ambulatory limbs, and the 

 abdomen. I have found it in much greater abundance on the abdomen 

 than elsewhere. B. astaci is found only on the gills. 

 Leipsic, Sept. 10. 1882. 



4. Zur Entwìckeiungsgeschichte der Ausfiihrungsgänge der Sexualdrüsen 



bei den Insecten. 



Von Joseph Nus bau m aus Warschau. 



Von meinem hochgeschätzten Lehrer, Herrn Prof. M. S. G an in, 

 angeregt, habe ich ausgedehnte Studien über die Entwickelungsge- 



