108 University of California Publications in Zoolorju [Vol. il 



in brackets) possessing the interval measuring 2.5-2.9 per cent 

 decreases as the length of animals increases, while the propor- 

 tion possessing the larger interval measuring 3.5-3.9 per cent 

 increases as the length of animals increases, it is evident that 

 there is a pronounced tendency toward positive correlation in 

 spite of the smallness of the coefficient (r= +0.165). Again, 

 the fact that the majority of animals between 16 and 22 mm. 

 have an interval measuring 2.5-2.9 per cent, while the majority 

 of those between 22 and 24 mm. have an interval of 3.0-3.4 per 

 cent, and the majority of those between 24 and 26 mm. have an 

 interval of 3.5-3.9 per cent — points once more toward positive 

 correlation. Finally, the following averages of interval measure- 

 ments, excepting that for animals 14 to 16 mm., increase with 

 considerable uniformity as the animals increase in length, point- 

 ing again toward positive correlation. Here are the averages: 



4.00 per cent for animals between ]4 and Ifinim 

 2..'i8 per cent for animals between 16 and IS mm 

 2.82 per cent for animals between 18 a ad 20 mm 

 3.0.5 per cent for animals between 20 and 22 mm 

 3.26 per cent for animals between 22 and 24 mm 

 3.36 jier cent for animals between 24 and 26 mm 



Length of Ov.vry. — Excepting the articles by Ritter-Zahouy 

 (1908, 1910) and myself (1911), nothing ha.s been published in 

 which the ovary has been considered of specific importance. Its 

 exclusion has been due to the fact that the ovary is the last 

 structure to develop, so that one could find ovaries of any size 

 in specimens otherwise fully mature. Nevertheless its average 

 and maximum extent and correlations with the length of animal, 

 as in table 6, reveal important characteri.stics for the species. 



While this table, together with the coefficient ()•= -|-0.S998), 

 shows that the ovary increases in length much faster than the 

 animal does, it also shows (1) that ovaries measuring less than 

 5 per cent were not found in animals over 1 6 mm. in length, 

 and (2) that ovaries mea,suring more than 15 per cent were not 

 found in animals under 22 mm. in length. Since we find (see 

 table 1) that the ovary does not reach maturity until its length 

 is over 20 per cent of that of the animal, these facts show that 



