92 MENSCH. [VOL. I. 



plane of new tissue formation, i.e., on the twelfth segment, has 

 followed the law of budding in this species and developed its 

 head from the tissues of the fourteenth segment, and thus added 

 two segments to the parent stock. The addition of new tissue 

 to the parent stock, after amputation of one or two of its pos- 

 terior segments, I have never been able to find in Proceraea, 

 and so far as I have been able to carry my observations, I am 

 convinced that such a condition does not take place, but that 

 instead, wherever new segments are formed 

 following amputation, the head takes its origin 

 from the tissues of the first new segment 

 formed. 



From these observations it would appear, 

 therefore, that by far the greatest variation 

 occurs in the chain-bearing form of Autolytus. 

 The great range in the position of the chain, 



q, TO, ii, old segments of 



parent stock; 12,13, and hence the amount of variation, is modified 

 of gC p^Tnt stock?"*! ^y a condition to which I have already referred 

 stolon with develop- j n a previous paper (Journal of Morphology, 



ing head. 



Vol. XVI, No. 2). I have there shown that 

 in this species, in the region in which new segments are being 

 formed (region of proliferation), not all the newly formed seg- 

 ments are pushed back for the formation of new stolons, but 

 that occasionally some of these segments become segments of 

 the parent stock, and thus considerably increase its length. In 

 this way I endeavor to account for the great length (40-58 

 segments) of the parent stock in the stouter and more devel- 

 oped specimens a length which I have shown does not exist in 

 the younger and more slender forms. This being the case, the 

 true range of variation would have to be sought in such speci- 

 mens only which are in the act of forming a first stolon by the 

 separation of the posterior segments of the parent stock. Of 

 such individuals I have found specimens sufficient to give a 

 range from segment 19 to as high as segment 38. Thus while 

 variation here, as identical with the mode of variation in the 

 species investigated, does not present so wide a range as indi- 

 cated in the tabulation, nevertheless it shows a far greater 

 range and is of much more frequent occurrence in chain-forming 



