26 DISCOVERY REPORTS 



distal block is block 2, 3 or 4. Nevertheless, the presence or absence of this granular strand is a 

 valuable indication of the relative maturity of the solitary form. The smallest specimens in which it 

 occurs provide evidence of the minimum body size at which chains of buds can be released, while the 

 number of buds present in the distal block is an indication of the potential number of aggregates that 

 can be released by one solitary individual at any one time. 



Data have been accumulated from the examinationof 287 specimens of 5. f^offz^ww? and 57 specimens 

 of S. gerlachei and the results are given in Table 6 and Text-fig. 9. Table 6 compares the mean number 

 of buds in block i (no strand) and block 2 (strand) with the body size of the specimen on which the 



300. 



Size group (mm.) 

 Block I 



80 100 o 20 40 60 8O 



BODY LENGTH Cmms) 



Text-fig. 9. Budding in 5. thompsoni and S. gerlachi. The mean number of buds produced in the first (shaded) and 

 second (unshaded) blocks of S. thompsoni and S. gerlachei plotted against body length. Full explanation in text. 



Table 6. The relationship between body length and budding in Salpa gerlachei and 



S. thompsoni. For full explanation see text. 



Total no. of 

 20-3030-40 40-50 50-60 60-70 70-80 80-90 90-100 loo-iio specimens 



S. gerlachei 



Mean number of buds 49-0 27-0 28-0 — — — — — — — 



Number obsv. 2 2 2 — — — — — — 6 



Block 2 Mean number of buds — i49'2 198-6 2236 229-0 240-0 240-0 — — — 



Number obsv. — ^ 5 20 14 8 3 i — — 51 



iS. thompsoni 



Block I Mean number of buds — 133-2 133-6 142-2 126-0 141-6 — — — — 



Number obsv. — 17 57 65 53 13 — — — 205 



Block 2 Mean number of buds — — — 174-6 i8i-2 207-2 2170 297-2 262-0 — 



Number obsv. — — — 3 18 31 19 7 4 82 



Mean number of buds in block i. S. gerlachei: 380 (6 obs.). 

 Mean number of buds in block i. S. thompsoni: 134-8 (205 obs.). 



count was made, the data being treated in size groups of 10 mm. interval. The data for S. gerlachei 

 are limited to specimens taken in a period from November to February and to eliminate seasonal 

 differences, if any, the S. thompsoni specimens are also from stations in these months. In plotting the 

 data in Text-fig. 9 it has been assumed that the distal block in those specimens with a strand is in 

 fact block 2 ; it is obvious from the results that this is probably not a valid assumption, particularly 

 for S. thompsoni; nevertheless, it in no way invalidates the argument that follows. 



The data in Table 6 and Text-fig. 9 show that there are a number of obvious differences between 

 S. thompsoni and S. gerlachei both in the number of buds initially produced — block i — and in the 

 size of the solitary form when this block is released. 





