260 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



growth of the lobster, really, takes place more or less throughout 

 the whole molting period. The growing tissue crowds against its 

 shell, finally the animal sheds this shell, the compressed tissues 

 expand and a rapid increase in size occurs. According to Herrick, 

 this swelling out of the body after the molt " is due to the absorption 

 of water through the new shell into the blood and tissues."* 



This fact that the increase in size is correlated with the molting 

 process, gives importance to the various factors which may influence 

 the frequency of the molting period, — such as light, temperature, 

 food, and the regeneration of injured structures. 



From the scientific standpoint the subject of regeneration is full 

 of interest. One of the most fundamental problems of biology at the 

 present time is to determine the relation and interactions existing 

 between different parts of the organism, and the phenomenon of 

 regeneration furnishes an opportunity to study these relations by 

 the experimental method. By disturbing the normal relations of the 

 different parts of the organic system, and noting the resultant 

 re-adjustments — as in the mutilation and regeneration of the appen- 

 dages of the lobster — we may both demonstrate the existence, and 

 learn something in regard to the nature, of these relations. 



In the molting habit of the lobster we have a phenomenon in 

 which the growing organism periodically reaches a climax and casts 

 off its outer shell or exoskeleton. In approaching this climax the 

 old tissue cells multiply and produce new^ tissue; the epithelial cells 

 in the skin secrete a second shell underneath the old one; and finally 

 these cell activities culminate in the act of molting. 



On the other hand, when a limb has been removed from the 

 lobster by mutilation, regeneration of that appendage occurs. In 

 the process of forming this new structure a second series of cellular 

 activities begins; which by multiplication and histological differen- 

 tiation results in the reconstruction of a complete new appendage. 



Accordingly, we have two distinct processes of cell activities. 

 The one, molting, is going on regularly, and more or less contin- 



*Herrick, Bulletin of U. S. Fish Commission, 1895, p. 81. 



