348 



KNOWLRDGK 



September, 1912. 



species, Rami claiiiata, R. sylvaticd .iiul R. I'lrcsccim 

 learned to avoid dis;ij;reeable objects, such as hairy 

 caterpillars, in from four to seven trials, and the h.abits 

 persisted for at least ten days. A Rtina clamata learned in 

 two tri.ils to avoid earthworms treated with chemicals, but the 

 " habit ■' persisted perfected for only a short time. When the 

 h.airy caterpillars were avoided, .active muscular rejection of 

 the caterpillar accompanied each trial ; but in the trials of the 

 chemically treated earthworms, no rejection, nor any muscular 

 action other than .ictive swallowing of the food, was observed. 

 "The latter habit was formed entirely within nervous tissue." 

 " The r.ipid formation of habits and the peculiar process of 

 examination observed while the habits were formed, indicate 

 intelligence of a relatively high order." 



HKARING IN FISHES.— Using the term "sounds" to 

 include any vibrations of the water, it may be said that 

 sounds aflect fishes through three sets of sense-organs — the 

 skin, the lateral-line organs, and the ears. Professor G. H. 

 Parker has made some interesting experiments and observa- 

 tions, particularly as to the eflfects of explosive sounds, such 

 as those produced by motor boats and guns. 



It has been shown within recent years that a fish can feel 

 sounds through its skin in much the same way as a man can 

 feel the vibrations of a musical instrument when his hand is 

 in contact with it. It has also been shown that some fishes 

 are awai'e by means of their lateral-line system of relatively 

 low vibrations, such as trembling movements of the water. 

 Thirdly, Professor Parker has convinced himself that the 

 internal ear is also an organ of hearing. This may seem a 

 gratuitous thing to prove, but only to those who are unaware 

 that there are many ears which are not hearing ears. The 

 ears of fishes have to do witli the adjustment of bodily motions 

 and equilibrium. 



" The sounds produced by motor boats are extremely faint 

 under water, and have little influence on the movements and 

 feeding of fishes. Such influence as they do have is temporary, 

 and very much restricted in local extent. Single explosive 

 sounds, like the report of a gun. may startle fishes and cause 

 them to cease feeding, but these responses are also temporary 

 and local, .'\lthough most sounds are repellent to fishes, some 

 may serve as lures to particular species." Fishes like the 

 Drumfish and the " Squeteague " produce noises which are, 

 without much doubt, concerned witli bringing the sexes 

 together at the breeding season. 



LOCOMOTION OF SEA-URCHIN.— Some thirty years 

 ago Romanes and Ewart pointed out that a sea-urchin uses 

 its lantern in progression out of water, and gave an account of 

 the manner in which the lantern acts. But this seems to have 

 been lost sight of. In 1910, Miss Abel, a student attending 

 one of the nature study classes at Millport Marine Station, 

 noticed that the sea-urchin given her to observe seemed to 

 move by lurches occurring at intervals, and that just prior to 

 each lurch the whole urchin rose up slightly from the surface 

 of the table. This observation was the starting-point of a 

 careful investigation by Dr. J. F. Gemmill into the locomotor 

 functions of Aristotle's lantern. 



" When travelling actively (out of water) the urchin raises 

 itself from time to time on the tips of its teeth in preparation 

 for a forward " step." The step is then accomplished by 

 means of (a) strong pushing or poling on the part of the 

 lantern ; (b) similar but usually weaker action on the part of 

 the spines ; (c) the influence of gravity acting at a certain 

 stage. After each " step " the lantern is retracted and swings 

 forward, so that the teeth come into position for initiating a 

 new " step." 



Under water the lantern is not needed for ordinary locomo- 

 tion, particularly over more or less horizontal surfaces. The 

 tube-feet and the spines are the effective agents. But it will 

 help if the urchins are loaded, or travelling up a slope on 

 certain surfaces, or only partially immersed, or mounting 

 rapidly up a vertical surface. 



" The locomotor .action of the lantern in urchins is a 

 particular manifestation of a rhythmic functional activity 

 which can also subserve feeding (no doubt the chief function). 



boring, and forced respiration. In .addition it possibly aids 

 the swallowing of food, the evacuation of faeces, and the 

 m.'iinlcnancc of physiological turgescence in v.irious internal 

 cavities." Filling of the gills takes place during retraction of 

 the lantern and emptying during protrusion. 



MECHANISM OF KESPIKATKJN IN INSECTS.— 

 When we watch a drone-fly, for instance, seated in the sun- 

 shine in the middle of a dandelion inflorescence, we notice 

 panting movements of the abdomen, — the expiratory move- 

 ments; for recent research, like that of Johann Kegen's, 

 fully confirms the old conclusion of Ratke and others — that 

 expiration in insects is the active process and is mainly due to 

 the contraction of abdominal muscles. The abdomen expands 

 again because of its elasticity and the air enters the tracheae 

 passively. It is an interesting instance of analogy that in 

 insects and in birds we should find the same peculiarity of 

 active expiration and passive inspiration, — so different from 

 what we are familiar with in our own body. 



COLOUR CHANGE IN SALAMANDER.— It has been 

 proved by Kammerer and others that the Spotted Salamander 

 (Salainandra maculosa) becomes almost black when the 

 soil of its vivarium is dark and relatively dry. Two things 

 happen : the yellow areas become gradually smaller, retreating 

 towards the centre until they disappear; and the dark areas 

 become darker. Experiments following the ordinary method 

 of exclusion, e.g., using a black-paper ground with normal 

 humidity, show that the shrinkage of the yellow spots is 

 affected by the colour of the ground, and the darkening by 

 increasing drought. Alois Gaisch relates in corroboration of 

 Kammerer's experiments that he put a salamander into a 

 vivarium with bl.ack peaty soil which remained moist, and 

 found it almost unrecognisable after three months. He gave 

 it a good bath, but it remained very dark. The yellow spots 

 had become much smaller and there were many black dots 

 about their margins. Microscopic examination showed that 

 black pigment had abundantly invaded the yellow areas. 

 An interesting fact, noted by Gaisch, is that two other 

 salamanders put in about the same time showed no change 

 of colour, which seems to show that there are differences in 

 individual susceptibility, perhaps in age-susceptibility. 



AMPHIBIANS OF THE GREAT COAL SWAMPS.— 

 The ancient forest-swamps of the Coal Era have meant much 

 to man, and their exploration has a unique interest. .Mr. 

 W. D. Matthew, of the American Museum of Natural History 

 has been telling us lately about Eryops. a prituitive Amphibian 

 which lived about the close of the Carb)oniferous Period — 

 " five times as old as Eohippiis, a hundred times as old as 

 the mammoth or mastodon or the earliest known remains of 

 man." It was " a sort of gigantic tadpole or mud puppy, with 

 wide flat head, no neck, a thick heavy body, short legs and 

 paddle-like feet and a heavy flattened tail." Heavy and 

 clumsy, small-brained and slow, it was near the top of the 

 genealogical tree in its day ! " The giant dragon fly that 

 darted over the head of the slow-crawling Eryops might seem, 

 except in size, a far superior type of being, a far more 

 promising candidate for the position of ancestor to the 

 intelligent life which was to appear in the dim future." But it 

 had reached the limit of great organisational change, while 

 " the amphibian was but beginning the adaptation of the 

 vertebrate structure to a terrestrial hfe." Perhaps the 

 possession of an internal instead of an external skeleton was, 

 as Professor Shaler suggested, an important feature in giving 

 free play to evolutionary potency which lay concealed in these 

 unpromising amphibians of the carboniferous swamps. 



HOW DOES A YOUNG BIRD BREAK THE EGG- 

 SHELL ? — The answer that rises to the lips is " By means 

 of its egg-tooth." But the bill and its egg-tooth are only the 

 instruments, wh.at about the musculature ? Franz Keibel has 

 inquired into this in the case of the chick and the duckling. 

 He finds that it is the musculus complexus that is actively 

 concerned, and that it is very markedly hypertrophied for some 

 time before hatching. On the tenth day after hatching it 

 shows no peculiarity. 



