Il6 THOS. MONTGOMERY, JR. 



2. Another spider made two cocoons, nos. 725 (8th August) 

 and 821 (i5th August). All the eggs of no. 725 (fixed at the 

 age of two hours and twenty minutes) were markedly larger than 

 any of the eggs of no. 821 (fixed at the moment of oviposition). 



3. Another spider made cocoons nos. 770 (iith August) and 

 905 (iSth August) ; the eggs of no. 770 (fixed at the age of 50 

 minutes) were all markedly smaller than the eggs of no. 904 

 (fixed at the age of 60^ hours). 



4. A fourth spider furnished cocoons no. 726 (8th August) and 

 no. 850 (i7th August). The eggs of no. 726 (fixed at the age 

 of 3 y 2 hours) were all markedly smaller than those of no. 850 

 (fixed at the age of 3 hours). 



The preceding series of cases show that successive cocoons 

 may have eggs of the same size ; or, and this is what more par- 

 ticularly interests us, that all the eggs of one may be larger or 

 smaller than all the eggs of another. It will be also noticed 

 (cases i and 4) that eggs of younger age may be larger than 

 eggs of maturer age. Indeed, there is probably no change in 

 the volume of a given egg from the time of oviposition up at 

 least to the time of appearance of the limbs ; accordingly, indi- 

 vidual growth of an egg is not a factor entering in to disturb our 

 conclusions as to these voluminal differences, since we are con- 

 sidering only stages antecedent to the appearance of limbs. 1 



To estimate the comparative egg volumina I placed the eggs 

 side by side under the lens, and judged their difference ocularly, 

 always comparing the smallest of a larger batch with the largest 

 of a smaller batch. It would not be possible to estimate relative 

 volumes by determining the number required to fill a given 

 space, without first dissecting off the envelopes of each egg. 



Now the variability of volume is usually of small amount in 

 any given cocoon, that is, all the eggs of a cocoon are large 

 or all small in most instances. But there are frequent excep- 

 tions to this. Thus one female produced three cocoons : nos. 

 722 (8th August), 800 ( 1 2th August) and 856 (i7th August), 

 all the eggs of no. 856 (fixed at the age of 26 hours) and 



1 During oviposition the eggs are polygonal, but usually within a few minutes all 

 become rounded (slightly ovoidal), as has been noted by Balbiani : Memoires sur le 

 developpement des Araneides, 1873. Bibl. de /' Ecole des Hautes Etudes, T. 7. 



