57 



Examining the different layers of the body-wall, we find, that the 

 epidermis in the caudal zone shows an entirely different structure as 

 in other body-segments, by the absence of the large glandular cells. 

 As proved by fig. 39 and 40, the epidermis on this spot consists of 

 slender, colummar cells, with an oblong oval nucleus, situated at 

 some distance from their base. I however cannot take this to be an 

 embryonic feature , as was done by Bbddaed ; for comparing it with the 

 epidermis of the zone of growth in Nais, Chaetogaster and Lum- 

 briculus f. i., we find there the epidermis modified in a layer of pro- 

 toplasma, wherein a great number of roundish nuclei lie in several 

 layers, densely crowded, no trace of cell- walls being visible. The mus- 

 cular layers too do not show an embryonic feature at all ; they are 

 not so thick and more stretched out as in the normal segments, 

 especially at the dorsal side, but this of course corresponds with the 

 dilated state of the caudal zone. The ventral nerve-cord, which, as 

 known , takes its origin from the ectoderm and in embryonic segments 

 is connected with it, has a completely normal character and the same 

 can be stated with regard to the wall of the intestinal canal. As to 

 the bristles , they are for the greater part absent , and those which are 

 present, are rather small; but it may be called in mind that in the 

 normal segments the setae also drop and are replaced by new ones , 

 and it may be suggested, that the dilated state of the caudal zone is 

 not well adapted for the preservation of the bristles. The characteristic 

 nephridial pores also did not show any signs of division or increase 

 in number, neither did the nephridia themselves nor the septa, as 

 was already pointed out by Bbddabd. Moreover I found in young exam- 

 ples, being only 20 m.m. in length, the number of segments nearly 

 complete, about 200, viz. 130 segments in front of the caudal zone, 

 and about 80 behind it. If really the increase of segments took place 

 in the caudal zone , in such young examples the number of segments 

 in the region behind that spot, ought to be much smaller. 



Though I regret not to be able to express an opinion as to the 

 real value of the caudal zone in P. corethrurus, I believe to have de- 

 monstrated, that there is no sufficient ground to accept the views of 

 Fb. Müller and Beddard, who look at the caudal zone as a place 

 of rapid growth ; and I am quite agreeing with Perrieb, who says about 

 this suggestion „ce serait une curieuse exception dans le groupe des 

 Lombriciens terrestres." 



