DEPARTMENT 01? MARINE BIOLOGY- 121 



under natural conditions, similar to the one now used in laboratory experi- 

 mentation upon animals, namely, that of using food as a stimulus. With the 

 "nest environment" as a stimulus, a variety of "problem boxes" was presented 

 to the adult terns, and the behavior of the birds noted as they, at successive 

 trials, gradually succeeded in overcoming the difficulties in the way of reach- 

 ing the nest. In this way the range of associations, the time of formation 

 of associations, the permanency of associations, etc., may be determined. On 

 account of the limited time, this work was carried only far enough to demon- 

 strate the feasibility of the method. 



(2) The young of both species were successfully reared by hand. Their 

 development was normal. Young so reared showed few signs of fear when 

 being experimented upon. Some of the work of Lloyd Morgan, Spaulding, 

 and others was verified. The most important observations in this connec- 

 tion were made upon the "perfection of instincts by habit" — many coordina- 

 tions were found to be imperfect at birth, but were rapidly perfected through 

 "trial and error." By keeping daily notes upon the development of the young 

 birds, a genetic statement of the rise and development of their instincts was 

 made possible. When the birds became sufficiently developed to withstand 

 a moderate degree of hunger, efforts were made to study their method of 

 forming associations. The simple maze of Porter (Amer. Jour. Psy., vol. 

 xvii^ pp. 248-271) was presented to both the noddies and the sooties. It was 

 learned by them in a time comparable to that of the pigeon in forming the 

 same association. Again, owing to the limitations of time, no wide range of 

 problems could be presented to the young birds. 



An effort was made to determine the distance to which the birds go in 

 obtaining their food. For the present, this distance is put tentatively at 

 about 15 knots. Distant orientation was tested in both species; 13 birds out 

 of 15 returned from distances varying from 17 knots to 740 knots. 



The work as a whole is mainly of interest in that it demonstrates the possi- 

 bility of conducting experiments upon the behavior of marine birds. 



Alfred G. Mayer continued the study of rhythmical pulsation and found 

 that in Cassiopea the stimulus which produces pulsation is maintained by the 

 diffuse nervous system of the subumbrella, and this stimulus causes the 

 muscles to contract. The stimulus will readily pass through tissue which has 

 recently regenerated and contains no muscles, or through parts wherein the 

 muscles have been rendered incapable of contracting through the action of 

 magnesium, distilled water, calcium, carbon dioxide, or alcohol. On the 

 other hand, the pulsation stimulus can not pass through, or be conducted by, 

 muscles from which the epithelial nervous network has been peeled away. 



Magnesium has but little effect upon the pulsation-stimulus, but it causes 

 relaxation and inertness in the muscles, and thus it renders the muscle rela- 

 tively incapable of responding to the nervous stimulus which causes contrac- 

 tion. Magnesium is, however, necessary for sustained pulsation, for without 

 it the muscles come into sustained tetanus of so pronounced a character that 

 the tissue is finally torn into shreds. This muscular tetanus is due to calcium, 

 as has been shown by Loeb. It is the role of magnesium to offset this effect 

 of calcium ; and thus the pulsating tissue is held in a state intermediate 



