,1)1(l l Johnson: Quantitative Study of Salpa chain. 173 



Though the individual series show irregularities, when the 

 mean is taken the results form an evenly graded series. 



There seems to be a compensation here, the full significance 

 of which is hard to see without a better knowledge of the nature 

 of the connection between the zooids and the manner of appro- 

 priation of the food supply. As the zooids stand in the chain, 

 the connection between a zooid and its neighbors in the same row 

 is less intimate than with its neighbors of the opposite row. For 

 this reason it is to be expected that the correlation should come 

 between the zooids of opposite rows rather than in neighboring 

 zooids of the same row. But apparently there is no reason for a 

 zooid pairing off with one of the two opposite zooids rather than 

 the other. 



GENERAL SUMMARY. 



This paper deals with the manner and rate of growth of the 

 zooids of a salpa chain. The observations were made chiefly upon 

 chains of Salpa fusiformis-runcinata. Brief examinations are 

 made of chains of Salpa zonaria-cordiformis and of Salpa 

 cylindrica. 



The subjects dealt with are (a) the species and its manner 

 of reproduction, (b) the form and structure of the chain, (c) the 

 method followed in taking measurements, (d) a discussion of 

 conclusions that can be drawn from the study. 



Some of the chief observations may be summarized as follows : 



1. The chain of Salpa fusiformis-runcinata is made up of a 

 series of blocks, the zooids of each block being approximately the 

 same size. 



