Io8 CURRENT LITERATURE. 



Mr. Hoyle finds that the kiminous organs of Ptcryslioteiithis inargaritifer 

 may be divided into four sets : i. Ocular, ii. Siphonal, iii. Branchial, and iv. 

 Abdominal. Of the first set there are nine on each eyeball, their arrangement 

 is irregular and there are marked differences in size ; the second set are two in 

 number, they are situated just below the hinder margin of the siphon ; the 

 third set are also paired, and lie at the root of each gill ; while the fourth set 

 are divided into a group of three lying transversely in the mantle cavity, close 

 to the anterior margin of the nidimental gland, and two lying one in front of 

 the other in the posterior end of the mantle cavity in the median line. As 

 regards structure, the ocular and siphonal are the most complex, the branchial 

 and abdominal being less so. Generally they recall the structure of the 

 luminous organs in other cephalopoda, described by this and other writers. 



Frandsen, P. — studies on the Reactions of Liinax luaxhniis to Directive 

 Stimuli. Amer. Ac. Arts and Sci., iQoi, vol. xxxvii, pp. 185-227, 22 figs. 



The behaviour of any organism toward artificial stimulation, the author 

 remarks, is probably always largely dependent on its normal environmental 

 conditions. The long action of these conditions, assisted, perhaps, by the 

 animal's own efforts, conscious or unconscious, to adapt itself to them, finally 

 results in certain habits and instincts. The process of adaptation being extremely 

 slow, organisms aie strongly averse to great or sudden changes in their environ- 

 ment and incapable of adjusting themselves to them. As a rule, then, we should 

 expect animals to seek those conditions of light, heat, moisture, and other physical 

 and chemical inHuences, which are most in accordance with those to which they 

 are normally subjected. 



In the present paper the author very carefully details his study of the 

 locomotor responses of Linuxx iiiaxiiiius to three kinds of stimuli ; those of touch, 

 gravity and light ; the chief results are as follows : Under ordinary circumstances, 

 the slug is negatively thigmotactic. On an inclined glass plate, all slugs give a 

 geotactic response, in some it is a decided positive, in others a markedly negative 

 response ; a few are somewhat indifferent. The quality and quantity of the 

 slime secreted, and the relative proportions of the length of the anterior and 

 posterior regions of the animal's body, are the two main factors in accounting 

 for the different responses. The animals are markedly phototactic, and as in 

 geotaxis, there are individual differences. To strong light, slugs, on the average 

 give a strong negative response ; the degree of response gradually diminishing 

 with the reduction in the strength of the stimulus. They are responsive to light 

 stimuli covering a wide range of intensities. In the dark, other directive stimuli 

 being eliminated, the slug tends to travel in a spiral of gradually increas- 

 ing radius, almost invariably producing one or more loops. These responses 

 to touch, gravity, and light-stimuli emphasise the fact, that it is an amimal's 

 normal environmental conditions which chiefly determines its general response 

 to artificial stimuli. The variations in precision and character of ihis general 

 response are mainly dependent on certain internal factors, such as the food 

 conditions of the animal, its fear of an enemy, and desire to escape captivity. 



EDITOR'S NOTES. 



Owing to the want of space, obituary notices of the late Alexander 

 Kowalevsky, Oliver Collett, and J. G. Cooper are held over until the December 

 issue. 



