56 



formed at this point." In a subsequent paper on the anatomy of 

 Diachaeta this opinion is also maintained. 



The worms, collected by Prop. Weber, being in an excellent state 

 of preservation , I resolved to examine this curious spot accurately and 

 to see if there really exists „a zone of growth," as suggested 

 by Fr. Müller and Beddard. 



In almost all our examples the caudal zone (it appears prefe 

 rable to me to make use of such an indifferent term, which prejudices 

 nothing about the morhological value of this body-region) is visible; 

 as stated by Fr. Müller, it lies always on a definite distance, about 

 130 segments according to Perrier, from the cephalic extremity. 

 If therefore really a formation of new segments takes place on this 

 spot, it can only be the case in the direction of the caudal 

 region. 



On examining the body-wall of the caudal zone on a glass-slide 

 (fig. 38) as a flat preparation in glycerine, we see, that six segments 

 are divided by a circular groove in two rings, which have each half 

 their longitudinal diameter. This division is not equally obvious over 

 the whole periphery of the body, because the grooves in the vicinity 

 of the ventral median line grow more or less inconspicuous. Lon- 

 gitudinal sections prove also (fig. 39), that these grooves are most 

 developed at the dorsal side, though even here they are sometimes 

 nothing but a shallow depression of the epidemis-layer; in the ven- 

 tral median region no signs of grooves are visible. 



The most striking feature of the body- wall in the caudal zone, is 

 the peculiar distribution of the bloodvessels; instead of 

 the net-work of fine capillary vessels , which occurs in other segments, 

 we find here in each segment two bands of large vessels closely crow- 

 ded together, each of them corresponding to a half segment. In the 

 ventral median region however this vessels are hardly discernible. 

 Transversal and longitudinal sections (fig. 40) learn us, that those 

 vessels are situated in the highly developed layer of connective tissue, 

 found between the layers of circular and longitudinal muscles. Though 

 I never detected bloodvessels in the epidermis itself, as stated by 

 Beddard, the red colour of the caudal zone during life, is doubtless 

 due to those bands of densely crowded vessels, and the suggestion 

 arises that on this spot an active respiration takes place and that 

 perhaps new elements are formed. 



