216 J. H. ORTON. 



A glance at the last column of Table 2 shows at once that the variation 

 in number of the gonadial tubes in this species is distributed sporadically 

 among individuals, and that the number does not necessarily increase 

 with the size of the adult animal. Since the number of gonadial tubes 

 is variable, it is of interest to examine the relative frequencies of the 

 occurrence of any particular number. The frequencies of particular 

 numbers, as, for example, of numbers between 10 and 15, and 16 and 20, 

 and so on, have been plotted to give the curve in Fig. 3, p. 217. As, 

 however, the number of individuals examined is small, the curve is less 

 symmetrical than it would probably have been if a thousand specimens 

 could have been examined. The ideal curve indicated by that in Fig. 3 

 would doubtless have one maximum in the region of 24 and 25, as indicated 

 by the dotted line. Whether, however, the smaller crest of the curve 

 (between 40 and 50) would become more important can only be found 



