622 GEORGE T. HARGITT 



entoderm cells bordering and extending into the developing bud 

 are distinctly the gastrovascular tissue of the medusa (fig. 40, 

 41, 45). At a similar point on the tentacle bulb of individuals 

 which are not producing medusa buds there is nothing to dis- 

 tinguish the tissues from those of any other part of the ten- 

 tacle. In other words the medusa buds take their origin from a 

 region of differentiated and specialized cells. 



But the cells of even the early outgrowths are distinctly of an 

 indifferent or embryonic character; the differentiated cells must, 

 therefore, undergo a modification, a regressive change, at the 

 time and in the place where the bud starts. Tissue cells in this 

 medusa must, therefore, have the capacity to give rise to em- 

 bryonic tissues capable of again differentiating into tissues spe- 

 cialized morphologically and physiologically. In short they may 

 produce new individuals with their varied cells, including germ 

 cells, for the germinal tissue arises from the same indifferent 

 tissue of the bud. Before the body cells may thus produce a 

 new individual they must undergo a dedifferentiation. 



Such a capacity of tissue cells may be interpreted by some 

 simply as an indication of their possession of that peculiar sub- 

 stance called germ plasm. There is no apparent reason why 

 such an explanation may not be given, though it obviously 

 broadens the significance of the term far beyond what was origi- 

 nally, and is still usually, given to it. It must be clear, however, 

 that if this is the significance of the term 'germ plasm,' or rather 

 if the term may be so broadened in its scope as to include this 

 concept, the term itself has no meaning and had better be 

 discarded. For such a capacity of cells as that described merely 

 means that tissue cells may produce a new generation either by 

 budding, or by first forming germ cells which in the usual man- 

 ner develop into a new individual. This is precisely the con- 

 clusion to which the study of this medusa and of other Coelen- 

 terates has led me. 



For those who desire to consider the indifferent cells of the 

 developing medusae as potential germ cells, since they are rather 

 embryonic in character, there is a further complication. In the 

 tentacle bulb, in the absence of developing medusae, no such 



