the Growth and Habits of Carausius morosus. 383 



Variation. 



Weismann, from a study of the variation of a partheno- 

 genetic organism, Cypris reptans, concluded (" Germ- 

 Plasm," 1893, p. 344) that forms reproduced in this manner 

 varied but little. He explained this comparative con- 

 stancy on the ground that the union of male and female 

 cells in sexually produced forms provided the material for 

 variation, and that, therefore, in the absence of the male 

 cell, greater stability in character resulted. Warren has 

 made observations on parthenogenetically reproduced speci- 

 mens of Daphnia magna, and found (Proc. Roy. Soc. lxv., 

 1899, p. 155) that the variation shown by them was very 

 considerable. In consequence of the divergent views on the 

 variability of parthenogenetic forms it seems desirable to 

 accumulate evidence on the subject, and the observations 

 made during this study of the life-history of Carausius 

 morosus are offered as a contribution towards that end. 



The observations made are summarised in the following 

 table, giving the maximum, minimum, range, average, 

 standard deviation and co-efficient of variation for each 

 character observed. The two latter are calculated on the 

 method advocated by Karl Pearson (" Grammar of Science," 

 2nd ed., p. 387). 



Table XVI. — Summary of Variations. 



Particulars of Observations. 



H:iii^o. 



Aver- 

 age. 



03 > 



Oviposition : Eggs produced per in- 

 sect 



Oviposition : Eggs produced per 



mm. length of insect .... 

 Size of Egg : Length in mm. 

 Incubation : Number of days . 

 Nymphs on hatching out : Length 



in mm 



Increase in length of Nymphs in 



mm. during first 24 horn's 

 Increase in length of Nymphs in 



mm. up to and at 1st moult . 

 Increase in length of Nymphs in 



mm. at 2nd moult .... 

 Increase in length of Nymphs in 



mm. at 3rd moult 



Increase in length of Nymphs in 



mm. at 4th moult 



Increase in length of Nymphs in 



mm. at 5th moult 



Increase in length of Nymphs in 



mm. at 6th moult 



Length of full-grown insects of one 



parent in mm 



Duration of Life : Number of days 



5-6 

 1-2 

 160 



6-5 



6 



5-75 



3 



2-5 



3-5 



6 



6 



11 

 194 



6-5 

 2-8 



165 



In-;, 



2-7 



9-9 



7-5 



9 



11-7 



1 l-l 



16-4 



80-1 

 361 



1-23 

 •16 



1U-S5 



1-34 



1-8 



1-23 



•77 



•75 



•87 



1-22 



1-68 



2-85 



40-48 



18-66 



18-92 



5-68 

 13-24 



12-7 



66-66 



L2-42 



10-2 



8-3 



7-43 



8-65 



LO-24 



3-55 



11-21 



