Cell-Theory jiot Sufficient for Explaining Organism 189 



tlie same time best authenticated instances of transfonination 

 of tissues accompanying the rej)laccment of lost parts has 

 been described by Nusbaum and Oxncr. The results of tlieir 

 researches significant for our present needs are sunmiarily 

 stated in the translation which follows: ""From what has 

 been said above, we see that in the regeneration of the an- 

 terior part of Linens lacteus, which has been robbed of the 

 entire old alimentary canal, the formation of new tissues 

 takes place heterogenetically in the highest measure ; tha^^ 

 is, it proceeds in such a w-ay that the new tissues arise from 

 an entirely strange old tissue from which they arc never 

 produced under normal conditions. We saw, that is to say, 

 that the epithelium of the entire new alimentary tract, a 

 tissue endodermal j)ar excellence, is formed in regeneration 

 by wander-cells which arise from tlie parenchyma and con- 

 nective tissue, therefore from a material originally wholly 

 mesodermal." ^ The elaborate description and illustration 

 with which they present their observations leaves little to be 

 desired for making the case trustworthy, even had it not 

 been confirmed by other workers. Fortunately, however, C. 

 Dawydoff, a Russian zoologist, working on the same species 

 at the same time but wholly independently, reached results 

 identical in every essential particular. 



Dawydoff's categorical statement touching the main point 

 is as follows : "The newly-arisen alimentary canal of Lin^us 

 lacteus is formed from mesoderm. It is differentiated from 

 the parenchyma and the walls of the lateral vessels." ^ A 

 very brief description of the experiment perfonned by these 

 investigators will suffice to make the crucial part of the 

 results clear. The nemertean has a long section of body 

 in front of the mouth, consequently into which no part of 

 the intestinal canal extends. From this it follows that if 

 the animal be cut in tw^o anterior to the mouth, the front 

 piece will be wholly devoid of digestive organs. Notwithstand- 

 ing this it was found that these gutless, mouthless pieces 



