576 



THE AMEBIC AN NATUEALIST 



[Vol. LI 



by experiment, we find that one cork will barely float say six 

 iron weights, corks with more than this number attached would 

 sink, while those with less attached would float. Moreover, if 

 those corks with more than six weights attached usually outnum- 

 bered those with less, while occasionally those with less far out- 

 numbered those with more, then both corks and iron weights 

 would be so distributed with respect to surface and bottom that, 

 while corks in the long run would be obtained in greater num- 

 bers from the surface than from the bottom, at least one would 

 be obtained in a greater percentage of bottom than of surface 

 hauls. In other words corks would be most abundant and least 

 frequent on the surface, while iron weights would be most abun- 

 dant and most frequent on the bottom— the exact parallel of the 

 distribution of the two generations of S. democratica. 



The conclusion, therefore, seems unescapable that the zooids, 

 after being pushed to the exterior on the proliferating stolon of 

 the solitary salpa, remain attached to each other and to the stolon 

 in the form of a protruding chain. 



More positive proof being mandatory, each of the seventy-six 

 hauls were carefully examined hut, although certain statistical 

 facts pointed toward .the existence of protruding chains, no two 

 zooids were found attached together. But, being convinced 

 against my own prejudice, that such chains were encountered 

 and broken up during the processes of towing and washing the 

 net, hauls of brief duration were made, and in some of them 

 several fragments of chains were discovered. Comparison of the 

 size of these zooids with that of the ]arg(\st ones found within the 

 test-cavity of the solitary sal[ia prnv(\s them to have remained 

 attached to their progenitor for a considerable period, probably 

 until at least one entire block of zooids had reached the exterior. 



The distributional data carry many other significant implica- 

 tions which can not be discussed in this limited time. Suffice it 

 to say that a complete report is now nearly ready for the press 

 and will be published in the Zoological series of the University 

 of California under the title "Differentials in Behavior of the 

 Two Generations of Salpa democratica Relative to the Tem- 

 perature of the Sea." 



iMjjs L. Mmi AKi. 



