March, 1913. 



KNOWLEDGE 



107 



process itself is simple and with ordinary care is capable of 

 giving good results, as is shown by the example. 



ADON TELEPHOTO LENSES.— We have received from 

 Messrs. J. H. Dallmeyer, Limited, a notice to the effect that 

 the manufacture of the "Junior Adon " lens has been discon- 

 tinued since February 1st, and that they will, therefore, be 

 unable to execute any further orders for them. The manu- 

 facture of the well-known adjustable form of Adon telephoto 

 lens, as well as the large Adons, working at F4- 5, F6 and F10, 

 for which the demand is very great, owing to the large scale 

 of pictures and simplicity of manipulation, will be continued 

 as before. The rapid fixed-focus Adons are meeting with 

 great success, not only in their use on reflex and other hand- 

 cameras, but as portrait lenses as well. 



ZOOLOGY. 



By Professor J. Arthur Thomson, M.A. 



FEEDING HABITS OF SERPENTS.— Raymond L. 

 Ditmars, curator of reptiles in the New York Zoological 

 Park, gives an interesting account of his observations on 

 the feeding habits of snakes. They are exceedingly captious 

 and sensitive. Changes of temperature and light, too much 

 public inspection, the artificial environment, and so on, affect 

 their nerves, and they go off their food on slight provocation. 

 None are vegetarian ; the majority like birds and mammals ; 

 a few are insectivorous ; the sea-snakes confine themselves to 

 fishes ; some eat frogs, lizards and other snakes ; some of the 

 smaller forms condescend to earthworms. There are many 

 specialisations in connection with feeding, one of the best 

 known being that of the African egg-eating snake, Dasypeltis 

 scabra, which swallows eggs three times the diameter of the 

 thickest part of its body. The jaws are almost toothless, but 

 a few posterior teeth enable them to grip the food. There is 

 alternate gripping and engulfing, and the egg slips into the 

 gullet. There it is cut by the knife-like points of the inferior 

 processes of the vertebrae which project into the gullet. By 

 this remarkable adaptation all wastage is avoided. The empty 

 shell is afterwards passed out again — an absolutely unique 

 habit. In other snakes that feed on eggs, the shells are 

 broken by the snake forcing its throat against the ground. 

 The fragments of the shell pass down to the stomach and are 

 quite dissolved. In the Indian Elachistodon westermanni 

 there is a structural adaptation similar to that of Dasypeltis, 

 but there seems to be no certainty as to its use. Mr. 

 Ditmars gives circumstantial details as to the diet of a 

 large number of types, and leaves us with a vivid impression 

 of the range of diversity in a single sub-class. What a 

 contrast, for instance, between the diminutive worm-snake 

 (Glaucoma) of tropical South America, which lies uncon- 

 cernedly inside the ant-hill devouring the larvae, and the huge 

 Boa or the Anaconda, lurking in the jungle growth along the 

 river banks on the watch for a passing peccary, capybara or 

 agouti. An interesting general point is that with few excep- 

 tions there is an abrupt and entire cessation of feeding on the 

 part of gravid females. 



A MOTH'S LOVE SIGNAL.— Many experiments have 

 been made to try to settle the much-discussed question 

 whether insects hear or not, but they have not yielded 

 satisfactory results, except in the way of showing that there 

 are many sounds to which insects which are credited with the 

 power of hearing pay no attention whatsoever. It is difficult, 

 however, to believe that all the instrumental music of crickets, 

 grasshoppers, cicadas, and the like falls on deaf ears ; and 

 Dr. Karl Peters suggests that the experiments that have yielded 

 negative results have been too much restricted to sounds that 

 have no biological significance to the creatures experimented 

 with. He gives an instance, which he has carefully 

 studied, which very strongly suggests that there may be 

 hearing in the strict sense, and that the production of a sound 

 may be utilised in love-making. 



His observations relate to an Alpine moth (Endrosa or 

 Setina aurita var. ratnosa) which is abundant at Arolla, at a 

 height of about two thousand five hundred metres. The males 

 fly about actively ; the females are sluggish and sit mostly 

 on the tussocks of grass, where they are very inconspicuous. 

 The males are able to produce a cracking noise, which is 

 peculiar to them, and the females respond to this, even when 

 they cannot see the males, by vibrating their body and wings. 

 The reaction on the female's part begins when the male flies 

 overhead or settles down close by ; it stops when the sound 

 stops. It seems difficult to avoid the conclusion that the 

 female hears the male's love signal. It seems likely that sight 

 plays a role on his part, and that the tremulous, vibrating 

 movements of the female attract his attention. 



RELATION OF HEART-WEIGHT TO MUSCULAR 

 EFFORT. — A. Magnan finds that birds with relatively small 

 wings and very numerous strokes per minute, have a relatively 

 heavier heart than those with larger wings and more sailing 

 power. Similarly, in Mammals, the proportion between weight 

 of heart and muscular development is greater in Carnivores 

 than in Herbivores. For while Herbivores can keep going a 

 long time they have not usually that capacity for intense 

 muscular effort which Carnivores show. It may be noted, 

 however, that Magnan does not deal with horse or chamois or 

 antelope, in which intense muscular effort is well known. It 

 is interesting to notice that the proportion in the deer, the 

 only large Herbivore measured, is more than double that of 

 the rabbit. The highest proportion is found in bats which 

 have such strongly developed pectoral muscles and " violent 

 effort in their flight." 



SLEEPING INSECTS. — Karl Fiebrig has made for many 

 years a study of insects (in Paraguay), which exhibit definite 

 sleep-attitudes, quite different from ordinary resting attitudes. 

 The insects remain motionless and stiff, as if in a trance. 

 Very characteristic is the clinching of the mandibles which 

 close upon the supporting object. The whole weight of the 

 body is often supported by the mandibles, no assistance 

 being given by limbs or wings. In many cases of "sleep" 

 the whole pose is unusual, being upside down or in some way 

 reyersed. The sleeping condition may be artificially induced 

 by changes in the illumination. When "asleep" the insects 

 are very callous as regards temperature, wind, touch and the 

 like. The sleeping pose is often of protective value. 



FIDDLER-CRABS. — A. S. Pearse has made an interesting 

 study of the fiddler-crabs (five species of Uca), which swarm 

 on the mud-flats at Manila. They live together in enormous 

 colonies, but there is no social life in the true sense. In fact, 

 they are extremely individualistic and pugnacious. " Each 

 individual jealously guards the area about his own burrow, 

 and immediately attacks any invader of this territory." The 

 burrow is the centre of activities, and the association for the 

 place where it is situated is very strong. The great chela of 

 the male is used as a weapon in fighting, and Mr. Pearse 

 cannot agree with Colonel Alcock that it is used as a signal to 

 charm and allure the females. A very interesting description 

 is given of the way in which the crabs carry mud away from 

 the burrow and close the opening with a plug when they go 

 into their retreat. 



NEW RHIZOCEPHALAN.— Mr. F. A. Potts describes 

 an extraordinary parasitic Crustacean, Mycetomorpha van- 

 couverensis n.g. et sp., a new representative of the Rhizoce- 

 phala. It occurs on the ventral surface of a shrimp, Crangon 

 communis, and has a flat mushroom-like body of a pale 

 yellow colour, with the borders fringed with numerous short 

 lobes. Colourless, absorptive roots extend into the host 

 below the nerve cord. The mantle cavity is full of Cypris 

 larvae. No trace of a male organ or of larval males was to 

 be seen, and it is suggested that the reproduction may be 

 parthenogenetic. The same may be true of Sylon and 

 Sesarmoxenos, two other strange Rhizocephala. 



