Jc'i.v. 1911. 



KNOWLEDGE. 



285 



is compensated for by means of a metallic thermometer which 

 iwists the spring of the unipivot galvanometer so as to 

 connteract the inaccuracy of the reading due to this change 

 of temperature of the cold junction. Thus the instrument 

 can be employed without any corrections to read conveniently 

 any temperature, being specially adaptable to the measurement 

 of low temperature, e.g.. refrigerators, and so on. 



The other instrument, the " Ampall" we must leave till next 

 month to describe. 



ZOOLOGY. 



By Professor J. Arthur Thomson, M.A. 



BIOLOGY OF A HAY I MUSION.— Everyone knows 

 that a ■■ hay infusion '" becomes a little world teeming with 

 animal and plant life, and that it goes through a cycle of 

 changes, form after form rising into dominance and then dis- 

 appearing. Professor L. L. Woodruff, who has made so 

 many interesting studies on Paraitioccitini, has begun a series 

 of precise studies on the biology of the hay-infusion, by 

 devoting himself particularly to what happens in the case of 

 this infusorian. " The interdependence of the organisms of a 

 hay infusion is so complex that, taken as a whole, it is almost 

 beyond the possibility of analysis, and accordingly the logical 

 method of approach to the subject is to study the interaction 

 of isolated organisms and small groups of organisms on them- 

 .selves and on each other." His first question was : " How is 

 Pitraiiioeciiini affected by different volumes of the culture 

 medium ? " and his answer is that the greater the \olume the 

 more rapid is the rate of division. He went on to enquire into 

 the effect of changing the culture-medium, and found evidence 

 that Paraiuoeciiini excretes substances which are toxic to itself 

 when present in its environment. These substances are more 

 effective when the organisms are confined in limited volumes 

 of culture fluid. These poisonous excretion-products play an 

 appreciable part in determining the period of maximum 

 numbers, the rate of decline, and so on. of Paraiitocciii m in 

 the " hay-infusions." 



AN INTERESTING MARINE HELIOZOON.— Some 

 years ago. Sassaki described a large Heliozoon. Gyiiino- 

 sphacra albida. which occurred in the salt water aquarium of 

 the Zoological Institute at Munich. It was supposed to 

 have been transported from Kovigno. Maurice Caullery has 

 been fortunate enough to rediscover Gyiiinospliaera on 

 seaweed at Banyuls, and he adds some notes to Sassaki's 

 description. It is a large Protozbon, easily visible to the 

 unaided eye ; it has long pseudopodia which sometimes 

 anastomose ; and it may have as many as twenty or thirty 

 nuclei. In some cases it armours itself with numerous 

 borrowed spicules of sponge and Holothurian. 



LUMINESCENCE OF FIRE-FLIES.— Notwithstanding 

 numerous investigations there seems to be still a great deal to 

 be discovered in connection with the luminescence of fire-flies. 

 F. A. McDermott and C. G. Crane have been recently studying 

 some of the American Lampyrids. They find practical 

 identity in the structure of the light-producing organs in these 

 beetles, which are popularly called fire-flies. The organ has 

 two layers, an inner one. white and opaque, which seems to 

 serve as a reflector, and perhaps protects the insect from its 

 own brightness, and an outer one, yellowish and translucent, 

 which is the seat of the actual photogenic process. 

 Physiological work led long .ago to the conclusion that the 

 photogenic process was of the nature of an oxidation, and this 

 is corroborated by the study of the structure, e.g.. by the 

 demonstration of the innumerable tracheae which penetrate 

 the organ. 



RHYTHMS OF ACTIVITY AMONG TERMITES.— 



It is probable that there is a rhythmic character in animal 

 activities to a greater extent than we as yet realise. Internal 

 rhythms have been established in the course of ages in 

 adaptation to external periodicities. But it does not, of 

 course, follow that there is greater activity during the day. 

 In a termites" nest, for instance, .Andrews and Middleton have 

 shown that there is about five times as much a-doing. as 

 expressed by the traffic in the arcades, in the greatest bustle 

 of night work as in the greatest ebb of noon. With great 

 patience they counted the comings in and goings out. " In 

 one case the number of termites going into the nest each hour 

 varied from 1,702 between 1 and 2 p.m. to 8,100 between 1 and 

 3 a.m., while in the same case the numbers going out of the 

 nest w-ere 1,194 between 12 and 1 noon, and fi,820 between 

 1 and 2 a.m." The curves show that the termites work at all 

 hours of day and night. Yet there are distinct rhythms in the 

 activities of the entire community. 



DISSEMINATION OF DISEASE BY HOUSE-FLIES. 

 — The part that is played by flies in disseminating tropical 

 diseases is well known, and our house-fly is a typhoid distribu- 

 tor. In regard to another common fly. the Biting P~ly 

 [Stomo.vys calcitrans\, it has been recently proved by 

 Prof. A. Schuberg and Dr. Ph. Kuhn that if it is itself 

 artificially infected with deadly Trypanosomes and Spirochaets, 

 it can transfer these to higher animals. 



SYMBIOTIC MICRO-ORGANISMS IN A CATER- 

 PILLAR. — In many animals there are minute inmates of the 

 food-canal which have a useful action on the food. There are, 

 for instance, some beautiful Infusorians which seem to be 

 always present in the horse's intestine, helping in the breaking 

 down of the hay and other food-stutfs. Some other animals 

 are known to have a friendly contingent of intestinal bacteria. 

 P. Portier has been working lately at the interesting caterpillar 

 of Xoiiagria typliae. which feeds inside the stem of bulrushes. 

 The digestive area is very restricted, and no ferment able to 

 digest cellulose could be found. But there was great 

 abundance of minute " pseudo-bacteria ", prob.ably small 

 moulds, which work at the vegetable tissue, breaking it 

 down. They pass through the wall of the intestine and are 

 engulfed bv the caterpillar's amoeboid blood corpuscles. The 

 case requiries further investigation, but it looks like a genuine 

 partnership, as if the "pseudo-bacteria" weie middle-men 

 between the animal and its food. 



MOUNTING MINUTE ARTHROPODS.— In spite of 

 many recipes it is often difficult to make a satisfactory business 

 of mounting minute Arthropods, such as small Diptera, 

 Hemiptera. and Acarines. Maurice Langeron recommends 

 very strongly the following method. He kills the specimens in 

 hot alcohol, and after a few minutes transfers them to 

 ■■ chloralphenol," either in a large drop on a slide or in a little 

 tube. This secures clearing and dehydration, and the 

 specimens can be transferred directly to balsam dissolved in 

 x\lol. The lluid that works so well is .Amann's chloralphenol. 

 It may be prepared by mixing two parts of hydrate of chloral 

 with one part of phenol, or by mixing equal parts of para-mono- 

 chlorophenol and hydrate of chloral. The mixtures are 

 liquefied at a gentle heat. 



INCUBATION OF CYCLAS EMBRYOS.— It is well- 

 known that these develop in the shelter of the inner gill-plate. 

 The incubatory sacs have been recently studied in detail by 

 PoyarkofI'. who brings out the interesting point that they are 

 in the main due to leucocytes. In other words, they arise by 

 a process analogous to inflammation and the gill-lamella 

 requires some patching afterwards, especially as regards its 

 ectodermic epithelium. 



44. COLOURS OF THE SPECTRUM.— Can the green 

 part of a spectrum be divided into yellow and blue ? If so. 

 how is it that the prism does not cause the vellow to fall 

 within the yellow limits, and the blue within the blue limits, 

 leaving the green position blank ? If not, can every colour 



OUF.RIHS, 



of a definite wave 



length be called .i " Primarv colour " ? 



H. T. 



45. HEAT .\ND A V.\CUUM.— If heat can travel over a 

 vacuum, how is it that a vacuum flask prevents a liquid from 

 cooling r H. F. 



