84 I'u'n-i'rsilfi of California Publications in Zoology. [Vol. 6 



pi. I). One might almost speak of these cell masses in this spe- 

 cies as "germs" of stigmata. One of the facts that I wish to call 

 attention to is that the substantive basis of the stigmata is the 

 border of epithelial cells around the orifice. Certainly as to 

 origin and probably as to later development the stigmata can 

 be adequately studied only by attending to these. 



For the first step in our next general inquiry we return to 

 the tentacles. In presenting the observations on the make-up 

 and development of these it was pointed out that of the primary 

 branches of the first generation, the earliest to appear probably, 

 and certainly the longest, occupy a place somewhat distal to 

 the middle point of the tentacle axis. (Fig. 13.) It was 

 pointed out also that these longer, and presumably earlier pri- 

 mary branches remain throughout the lifetime of the individual 

 longer and more elaborately branched than the later primary 

 branches which arise both distally and proximately from them. 

 Another way of expressing the fact is by saying that later formed 

 primary branches of any generation never catch up in size 

 with those coming on immediately before them. Attention was 

 further called to the fact that in general the beginning and sub- 

 sequent growth and development of secondary branches of one 

 generation hold the same relation to their primary axes that the 

 primary branches hold to the tentacular axes. And it was point- 

 ed out that typically the tertiary branches also have the same 

 relation to the axes of the secondary branches. Now come sev- 

 eral elosely connected and exceedingly far-jeaching questions 

 about the multiplication of parts in these tentacles. The first 

 may In- put in the following form: Is there a rule or law accord- 

 ing to which the branches of any given generation pertaining to 

 any given axis diminish in length after their growth is com- 

 pleted .' Almost certainly there is. Simple inspection of the pri- 

 mary branches of generation 1, for example, in the young ten- 

 tacle shown in figure 13 seems to recognize such to lie the ca e. 

 If this lie so. then there comes immediately another quest >n, 

 namely: Does the same rule hold for all the tentacles, and for all 

 the orders of branches of all the tentacles? One should not fail 

 to perceive that a law of diminution in length of branches for a 



