1910] 



Johnson: Quantitativt Study of Salpa Chain. 



147 



With the salpa chain, on the other hand, the problem is one 

 of growth, for we are considering size relations in a repetitive 

 series of den lupiiif/ parts. 



The working out of the problem as well as the summing up 

 of results has been done under the direction of Professor Wni. 

 E. Ritter of the University of California. Dr. Pearl has assisted 

 in the treatment of some of the data. Professor A. \Y. Whitney 

 and Mr. Joseph Lipke of the mathematics department of the 

 University of California have also given helpful advice in the 

 mathematical work. 



2. THE MATERIAL. 



The material used was from collections made at the Marine 

 Biological Station at La Jolla, California. Salpa fusiformis- 

 runcinata, the species chiefly employed, occurs there in large 



Fig. 1. — S. fusiformis runeinata — asexual 

 branchial orifice; at., atrial orifice; ch., chain. 



solitary generation: ~br 



numbers during the summer months, especially during June and 

 July. At this time individuals of all sizes are taken and well 

 developed chains are found in almost all of the solitary genera- 

 tion. 



A general description of the species, especially of its manner 

 of asexual reproduction, is the first essential to a clear under- 

 standing of the problem. 



The salpae are notable for their two generations. The one 

 known as the "solitary" oeneration (Pig. 1) produces offspring 

 asexually by budding. The buds are arranged in chains which 

 are sometimes circular and sometimes linear. These buds, when 



