78 



KNOWLEDGE. 



Feuruarv. 1911. 



disagreeable taste, which sometimes makes them almost 

 uneatable. The taste is called "' iiiuddj'," but Louis Leger's 

 experiments have shown that it is not directly due to the mud. 

 The Stonewort 'iChara), which has a curious odour, has 

 been blamed, but Leger has shown that the "muddy" taste 

 may occur in fishes from basins without any stonewort. 

 Following the method of excUision. he has traced the mischief 

 to Oscillarias, those curious mobile Algae, which are common 

 in fresh waters. They are directly or indirecth' used by the 

 fishes as food, and it is their " essence " that saturates through 

 the fish-body. The taste is strongest in the glandular parts of 

 tbe sUin and in the kidneys. Carnivorous fishes are less liable 

 to be tainted, but even trout do not escape. 



A NEW CO>r'>iEN"SAL TURBELLARIAX. — Professor 

 Edwin Lin'"- ;,'and in the ribbed mussel {Modiolus 

 plicatiilii .: A'oods Hole an abundant occurrence of a 

 comment. i 'i ^ele Turbellarian, belonging to the genus 



GraiplJi\ ' .1 ' losely-relaled genus. It is interesting in 



many ways, e.g., in containing ciliated young, most of which 

 were in t'm'os inside a thin capsular envelope. The young are 

 not liberated until the reproductive powers of the mother are 

 exhausted, when they make their way through the ruptured 

 body-wall. Another interesting peculiarity is that the adults, 

 which rarely reach 2mm. in length, move by a series of zi.g-zags, 

 — a mode of progression which affords constant change of 

 position within the limited area of the host. 



DO BLOW-FLY LARVAE RESPOND TO GRAVITY?— 

 S. O. Mast has investigated Professor Jacques Loeb's statement 

 that blow-fly larvae " when placed under the surface of the 

 water, do not swim upwards and so avoid death, but swim 

 downwards." It is found, however, that blow-fly larvae do 

 not react to gravity, either in water or out of it. In air they 

 may be found to crawl nearly straight upwards on objects, but 

 experiments show that this has no relation to gravity. In 

 water they sink to the bottom or float at the top according to 

 the amount of gas they contain, and there is no evidence 

 whatever indicating that they can swim. 



PROCESSION CATERPILLARS.— A month or two ago 

 we described observations on the habits of the Procession 

 Caterpillar. Cncthocampns pinivora, made at Arcachon by 

 Mr. T. G. Edwards in the Spring of 1909. An account of 

 additional observations and experiments made in the following 

 Spring is now published by Mr. H. H. Brindley. Strangely 

 enough, the greater number of the processions seen by 

 -Mr. Brindley were met, not within the forest itself, but on a 

 broad road (over which there was constant traffic) leading 

 towards it. The road was bordered by \illas, in many of the 

 gardens of which there were pine trees. Many nests containing 

 living larvae were found on the young pine saplings in the 

 forest, and in all cases the branches near the nest were thickly 

 matted with the threads secreted by the larvae. Very few 

 threads were found on the branches at a lower level, or on 

 the trunk, and of these none reached the ground, so that the 

 threads gave no evidence that the larvae were in the habit of 

 leaving the nest and returning to it. A series of experiments 

 with the thread showed that it has no great importance in 

 the formation of the procession, or even in keeping it together. 

 Head to tail contact seems the important factor, and when 

 that is broken, the detached portion of the procession joins on 

 again, apparently by sight, if the distance is not great. 

 The thread forms the nest in the tree, and the cocoon in the 

 pupa state, but it is not clear why it should continue to be 

 formed when the larva is away from the nest, unless it is to be 

 regarded as a mere secretion. Mr. Brindley made an interest- 

 ing series of experiments to test the permanency of the 

 leadership. In small processions, each individual caterpillar 

 was dusted with a powder of a different colour, and the pro- 

 cession was interrupted. In fifty per cent, of cases the same 

 leader took the head of the procession, whether mass-formation 

 was natural or artificial ; the leader for the time being 

 undoubtedly determining the behaviour of the procession, since 

 contact is always maintained. The leader always takes the 

 initiative in mass-formation and very frequently in burrowing. 



The observer did not experience any irritation on handling 

 the caterpillars, and he believes, with his collaborator, that the 



degree of sensibility to the glandular hairs \aries with the 

 individual. 



YAWNING IN FISHES.— Mr. Richard Elmhirst. 

 Superintendent of the Millport Marine Biological Station, has 

 made some \ery interesting observations on Yawning in Fishes. 

 He has watched it in cod, saithe. cobbler, plaice, and some 

 others. He describes the wide opening of the mouth, the slow 

 expansion of the buccal cavity, the erection of the gill-arches, 

 and then a rapid expulsion of the indrawn water, mostly from 

 the mouth, partly through the gill-slits. This is often 

 accompanied by a distinct heaving of the pectoral region and 

 erection of the pectoral fins, and is quite different from the 

 rapid movement of the gill-cover and jaws when the fish 

 dislodges a bit of seaweed from its gills. " From numerous 

 observations, I am led to think that this action of fishes is a 

 real yawn, and serves the true ph\-siological purpose of a 

 yawn, i.e., flushing the brain with blood during periods of 

 sluggishness. The conditions conducive to yawning are a 

 slight increase in the temperature of the water, and. I suppose, 

 the accompanying dimhmtion of oxygen." 



A NEW KIND OF SENSE ORGAN.— As anatomical 

 analysis becomes more and more minute there is a continual 

 discovery of new intricacies. A good illustration is to be 

 found in an investigation which Dr. K. W. Dammermaun has 

 recently been engaged in, concerning the saccus vasculosus. a 

 dependence of the brain peculiar to fishes. It will be 

 remembered that there is a remarkable downgrowth, or 

 infundibulum. from the tween-brain or region of the optic 

 thalami (the part of the brain that also gives origin to the 

 pineal body as a dorsal upgrowth 1. This infundibulum bears 

 the very interesting pituitary body, but it also gives off a 

 posterior diverticulum called the saccus vasculosus. In many 

 fishes this extends backwards and lies, along with the pituitary 

 body, in a pit of the skull called the sella turcica. It has been 

 usually regarded as a glandular structure, but Dammermann 

 has proved up to the hilt, what a few have suspected, that it is 

 a sensory organ with somewhat striking sense-cells. In an 

 ingenious argument he suggests that it may enable the fish to 

 test the degree of oxygenation in the water, and thus to seek 

 out the depth physiologically most comfortable. He proposes 

 to call it a " Benthic " or Depth-Organ. 



EVOLUTION OF REPTILIAN ARMATURE.- Georg 

 Stehli has been studying the development of scales (in the wide 

 sense) in various reptiles, and comparing recent with extinct 

 forms. He is strongly of the view, also held by Hase and 

 Otto, that the scales had primitively a segmental arrangement, 

 and that each horny scale belonged primitively to an under- 

 lying bony scale. His theory is that the evolution of reptilian 

 armour has passed through four stages. First, there was the 

 primitive stage (which must, of course, have had a long evolution 

 behind it) of strictly segmental arrangement of horny scales 

 with bony scales beneath them. In some cases doubling gave 

 rise to two rings of scales for each segment. Secondly, the 

 bony scale broke up into a mosaic of little plates, as seen 

 to-day in Scincoid lizards. Thirdly, the bony scale disappeared. 

 Fourthly, the horny scales multiplied and lost their segmental 

 arrangement. 



A QUAINT STRUCTURAL ANALOGY.- One might 

 spend a pleasant life-time in admiring organic adaptations. 

 One of the last we have read about concerns the "snow-shoes" 

 of the North-American ruffed grouse (Bonasa iDiihcUata). 

 According to Dr. Austin Hobart Clark, these " snow-shoes " 

 de\ elop in winter as two rows of '' scutes " on each side of 

 each toe. and they increase the area of the foot by as much 

 again. Thus the bird treads safely on the lightly-compacted 

 snow. It might be interesting to test experimentally whether 

 the stimulus of wet feet at some other season than winter 

 would induce the extra integumentary growth. Dr. Clark 

 points out that a figure of the ruffed grouse's toe is very much 

 the same as a figure of the arm of some of the Crinoids from 

 deeper waters. Two rows of supplementary plates occur on 

 each side of the median row, and the meaning of the adapta- 

 tion is to increase the receptive surface on which the shower 

 of minute dead organisms is caught. Convergent adaptation 

 in two creatures ahnost literally as far as the poles apart ! 



