GENERAL BIOLOGY 755 



have been carried there by the currents from distant spawning 

 grounds, just as the herrings are carried to the coasts of 

 northern Norway from distant spawning grounds on the 

 North Sea coast, or as the young cod of northern Iceland have 

 drifted from the south coast of that island. This result is in 

 itself of great importance, contributing to our knowledge of the 

 mysterious life-history of the eel, especially when viewed 

 together with similar facts pertaining to other leptocephali 

 (conger, Synapkobrancktis), and to forms like A7'gyropelecus, 

 Scopelidae, etc., which were far more numerous on our southern 

 than on our northern track. Just as all the tropical and warm 

 water forms, from foraminifera and copepoda to fishes, occur 

 mainly south of the 40th degree, so also is the spawning of 

 warm water fishes limited to this same area. I therefore 

 believe that the eel probably belongs to this " intermediate " 

 group, of which one is reminded by the large eyes and the 

 silvery sheen of migrating "ripe" eels (compare, for instance, 

 Serrivomer). 



I am inclined to explain the fact that we did not obtain 

 many of the remarkable larvae and young fish collected by 

 other expeditions from the surface of the ocean, as recorded for 

 instance by Llitken in his Spolia Atlantica, by supposing 

 that we did not go far enough south. Llitken states that his 

 small young swordfish were all captured in tropical localities, and 

 in regard to the mackerel he quotes Captain Andrea thus : 

 "The Bonito is the oceanic fish which I have most frequently 

 seen and captured; it is seen everywhere in the North and South 

 Atlantic between the tropics, increasing in abundance as one 

 approaches the equator. In the Indian Ocean I have not seen 

 it south of lat. 26^ S. nor east of long. 70° E. In the Java Sea, 

 the China Sea, the Yellow Sea, and the Japan Sea I have 

 never observed it." 



In this place I have limited my remarks to the fishes alone, 

 but similar results would probably appear in most animal groups 

 if their vertical and horizontal distribution were studied ; this 

 must be reserved for the future, when the material collected by 

 the expedition has been examined in detail. 



Age and Growth 



It has long been recognised that there is a certain correlation 

 between the size and the age of animals belonging to the same 

 species, and that a definite increment in size takes place within 



