DEPARTMENT OF MARINE BIOLOGY. 201 



Early in the spring of 1915 a passing fisherman reported white rats on 

 East Key. In the summer of 1915 four were caught with spring traps, just 

 to make certain that the rats were there. In May 1916 one was taken in 

 a spring trap. It was preserved in formalin and subsequent examination 

 showed that it was an animal of good size, but with infected lungs. At the 

 invitation of Dr. Mayer, Dr. Hatai and myself went to the Tortugas Station 

 in June of this year (1916) to make a study of the rats on East Key. One 

 female was caught by us. There were fetuses at the 10-day stage in the 

 uterus. This indicated the presence of a surviving male, but our efforts to 

 trap more rats failed. When it became evident that the number of rats on 

 East Key must be very small, a fresh lot of animals was sent to the Tortugas 

 Station from the Wistar Institute. From this lot, which came through with 

 only one death, 30 pairs were placed on East Key and 11 males and 13 females 

 on Garden Key. Both groups were ear-marked. Ten days after their 

 release albinos were observed on both of these keys, and no dead were seen. 

 These two groups will be studied during another season. 



East Key is oval in shape and about 300 yards long, and is moderately 

 covered with brush. There is no fresh water to be obtained, except from 

 rain and dew. The available food is mainly furnished by the sea oat and 

 other grasses, the Ocypoda crab, and materials washed ashore. Our results 

 show that under these conditions the albino rat is able to persist on East 

 Key for a trifle over 2 years, and that the last one caught was pregnant. 

 If no new litters had been reared during the two years' interval, then we 

 have caught in all 6 out of the original 8 rats, and at least 1 male must have 

 remained uncaught. The eighth animal is not accounted for. 



The one female which was caught on East Key after our arrival at the 

 Tortugas Station showed normal bodily proportions and had a weight of brain 

 and of spinal cord almost precisely that to be expected in an animal of this 

 size. However, we can not say whether this rat belonged to the original 

 lot or whether she was bred on the Key. 



The influence of the wild life would be expected to show only in the 

 descendants, so that several generations will be required to determine 

 whether a change has been effected. The lot brought to the Tortugas from 

 Philadelphia this year was decidedly affected by the journey of four days, 

 the relative weights of several of the important viscera and glands being 

 much modified. In every animal examined the spleen was from two to 

 three times its normal size; the percentage of water in the nervous system 

 was also increased; but within ten days after their arrival at the Tortugas, 

 rats which had been kept under favorable conditions in the laboratory 

 showed a return of the modified organs to the normal relations. 



It is to be noted that the house rat (Mus alexandrinus) lives under the 

 Tortugas conditions and is found on Garden Key, Bird Key, and Logger- 

 head Key, having been brought by ships. In earlier years it was present 

 in large numbers on Loggerhead Key. As Mus alexandrinus does not cross 

 with the albino of Mus norvegicus, the presence of the former is not regarded 

 as a disturbing factor for the present experiment. 



Experimental Studies upon the Aging and Death of Germ-Cells, 

 by A. J. Goldfarh. 



Last year's studies with the sea-urchin, Toxopneustes variegatus, showed 

 that certain profound alterations take place with increasing staleness of eggs 

 and sperm. These changes may conveniently be grouped under three head- 

 ings: (1) a lowered percentage of eggs capable of being fertiKzed; (2) a modi- 

 fied rate and a change in the character of the fertilization membrane; (3) a 



