DEPARTMENT OF MARINE BIOLOGY. 179 



No albinos were recovered from Garden Key. 



From East Key, between June 29 and July 22, 7 albinos (2 males, 5 females) 

 were obtained; 2 were killed in capture and only the body measurements of 

 these could be obtained ; 5 were taken alive, and for these the body measure- 

 ments and the weights of the brain, spinal cord, the several ductless glands 

 and the gonads were recorded. These results showed that some of the 60 

 rats (30 pairs) placed on East Key in 1916 had survived. Among the 7 there 

 were 2 small animals (body-weights 36 gm. and 56.7 gm.) which were not ear- 

 marked. These must have been born on the key. The 1916 rats therefore 

 bred during their stay on the key. 



Our third question relates to the weight of the central nervous system and 

 some of the other organs. 



Before the rats were released last year, a sample series of 3 males and 3 

 females was examined for the weights of the several organs. In these ani- 

 mals, which we assume to have been similar to those released, the brain was 

 2 per cent heavy, the cord 3 per cent light, while the suprarenals were heavy, 

 the gonads somewhat heavy, and the thymus and thyroid very light. 



In the 5 captured rats examined for the weights of the organs, the relative 

 weight of the brain was found to be 6 per cent and of the spinal cord 4 per cent 

 above the standard values for albinos of the same body-lengths, while the 

 weight relations of the ductless glands and gonads corresponded to those of 

 the rats when released. In this series of 5, 1 rat had been born on the key, 

 but the values for the organs in this animal stood in the same relation to the 

 standard values as in the case of the other 4. Characteristic of all the rats 

 was the very small weight of the thyroid gland. Our main interest in these 

 results is connected with the relative weight of the brain and spinal cord. In 

 all of the 5 cases the brain-weight found was higher than that to be expected, 

 while in 4 out of the 5 cases the same was true for the weight of the spinal cord. 

 Apparently life under wild conditions tends to increase the relative weight of 

 the central nervous system, even when the rat is 100 days old before being 

 subjected to the new environment. 



The conditions on East Key are severe. Rain and dew are the only sources 

 of fresh water, yet one captured rat refused to drink when fresh water was 

 offered to it. The main food-supply seems to be sea-oats and the ocypoda 

 crabs, both of which were found much reduced in quantity this summer as 

 compared with last summer. 



The old rats (5 in number) all had infected lungs; the 2 young rats sound 

 lungs. 



The rats were tame, in the sense of not fearing man, so that several were 

 caught with a butterfly net. On the other hand, the two males, when put 

 together, fought savagely. 



There is no reason to think that the supply of these rats on East Key has 

 been exhausted, and possibly a later visit to this key will reveal full-grown 

 descendants of the original lot. It is in these descendants that we should 

 expect to find more clearly marked the effects of feralization if this condition 



really produces definite modifications. 



"^ 



The Brain Weight of the Gray Snapper, NeomcEnis griseus, of Different Body- 

 lengths; and also a Determination of the Various Nitrogenous Extractive 

 Substances in the Brain, hy S. Hatai. 



The primary object of the present investigation was to extend'some observa- 

 tions made on the central nervous system of the albino rat to the nervous 

 system of lower vertebrates. There has been much speculation from time to 

 time by various writers concerning the metabolic activity of this important 



