Cell-Theory not Sufficient for Explaining Organism 189 



the same time best authenticated instances of transfonnation 

 of tissues accompanjing- the replacement of lost parts has 

 been described by Nusbaum and Oxner. The results of their 

 researches significant for our present needs are summarily 

 stated in the translation wliich follows : '"From what has 

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

 terior part of Linens lactcn.s, which has been robbed of the 

 entire old alimentary canal, the formatioji of new tissues 

 takes place heterogenetically in the highest measure ; that 

 is, it proceeds in such a way that the new tissues arise from 

 an entirely strange old tissue from which they are never 

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

 that the epithelium of the entire new alimentary tract, a 

 tissue endodermal 2^(f^' excellence, is formed in regeneration 

 by wander-cells which arise from tlie })arenchvma and con- 

 nective tissue, therefore from a material originally wholly 

 mesodermal." ^ The elaborate description and illustratif)n 

 with which they present their observations leaves little to be 

 desired for making- the case trustworthv, 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 ])oint 

 is as follow.5 : "The newly-arisen alimentary canal of Linens 

 lacteus is formed from mesoderm. It is differentiated from 

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

 very brief description of the ex])erlment performed 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 two 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 



