444 Thos. H. Montgomery, 'Jr. 



From these data we infer the following conclusions: 



1 The average male ratio (number of the males divided by 

 the number of the females) is 8.19, determined from a count of 

 41,749 newly hatched spiderlings. Among the progeny of a par- 

 ticular female this ratio was never lower than 1.2 nor higher than 

 27.5. To a cocoon the average number of hatched males is 292.9, 

 of hatched females, 35.7, and of unhatched eggs, 22.6; the average 

 number of eggs to a cocoon is 351.2. Of the total of 127 cocoons 

 entered in this computation, only 8 showed a male ratio of less than 

 one, and from only one (2016M) did only males emerge and 

 no females, this being the only "unisexual" cocoon. The highest 

 male ratio in any cocoon, excluding the case of 2016M just cited 

 was 202 (in 2003B); in eighteen cocoons the male ratio was 30 or 

 higher. 



2 The objection might be raised that the above average male 

 ratio of 8.19 might not be the normal one for the species, but might 

 be induced by the life of captivity of the mothers. Therefore I 

 have considered separately the ratio in cocoons made in the natural 

 state and brought into my study to hatch out. Such cocoons are 

 the following of Table I: 2008A, 2012A, 2013A, 2014A, 2015A, 

 2020B, 2022A, 2030A, 203 1 A. These present a total of 3866 

 males and 223 females, giving the average male ratio of 17.3, con- 

 siderably higher than the ratio 8.19 obtained from the total of 

 cocoons I raised. Whether this difference is due to difference in 

 the mode of life of the mothers, or rather so the fact (to be brought 

 out later) that the male ratio tends to be highest in the first cocoon 

 of a series, I cannot say. These figures would show at least that 

 the high male ratio of captive cocoons cannot be ascribed to 

 artificial conditions, and indeed there is no reason for thinking 

 that the imprisonment of the mothers could affect this ratio. 



3 It will be noticed that the male ratio was determined for 

 each cocoon, accordingly also for the average of all cocoons, from 

 the spiderHngs that hatched out because I could not distinguish 

 the sexes before the time of hatching. That is, the male ratio of 

 those eggs that did not hatch could not be ascertained, and this 

 is the single disturbing error in the above calculations. Table I 

 furnishes the number of unhatched eggs for each cocoon, and 



