HETEROMORPHOSIS 149 



incision &, while none have grown from the incision c near 

 the foot end, even though the lips of the wound were pre- 

 vented from healing together. In the drawing which was 

 made from life, the cut is relatively far removed from the 

 foot end of the animal. This is because the aboral end cd 

 lying behind the second cut is greatly stretched, while that 

 portion of the animal lying anterior to the incision is con- 

 tracted. It will also be seen that after such an incision both 

 parts become independent of each other to a certain extent; 

 much as after transverse section of the spinal cord in one of 

 the higher animals the incision renders the two parts of the 

 animal comparatively independent. 



3. I found no statement in the literature as to whether or 

 not such observations had already been made upon other 

 animals. It is, however, known that a new Hydra may spring 

 from the body of an old one, which increases in size, and 

 after a certain time separates from the mother to lead an 

 individual existence. As long as it remains attached to the 

 mother, the whole is to be regarded as an animal with two 

 heads situated one above the other; for the body cavities of 

 the young and the old animal communicate with each 

 other. Yet such a Hydra is essentially different from our 

 Cerianthus. While in Hydra not only a head, but a whole 

 body is formed, only the oral plate is formed in Cerianthus. 

 While the new animal becomes detached after some time in 

 Hydra, the new head in Cerianthus remains permanently 

 attached to the mother. Furthermore, while in Hydra the 

 newly formed individual has the same number of tentacles, 

 and the same cylindrical form as the mother, the number of 

 tentacles that grow in Cerianthus is dependent upon the size 

 of the incision. The smaller the incision, the smaller is the 

 number of tentacles that are formed. Only a segment of a 

 head, corresponding to the size of the incision, is therefore 

 formed when an incision is made into a Cerianthus. A 



