August 21, 1891.] 



SCIENCE. 



lOI 



lectures on experimental and practical medicine, classified the re- 

 sults of most of these previous authors, and tested them by a new 

 series of direct observations. Ris table of mean results showed 

 that vegetable feeders have a high temperature. The sheep gave 

 a temperature of 104°, the goat of 104°, the pigeon of 108", and 

 the common fowl 108°. The rabbit showed 103°, while the dog 

 and the cat, animal or mixed feeders, showed 103°. But some 

 herbivora were comparatively low, the ox, for example, 101°, and 

 the horse 100". The differences here stated were supposed by the 

 last-named observer to depend on the cutaneous covering of the 

 animal more than on any other cause. In the case of the pigeon, 

 on which this author made ninety-four observations, the high tem- 

 perature was attributed to the non-conducting character of the 

 feathers, a marvellous protection to a swift-flying animal in a cold 

 atmosphere. In man, from 100 observations, he came to the con- 

 clusion that in a strictly natural state 98° F. was the truest stan- 

 dard. These researches are useful as comparative studies; still, it 

 is an open question whether in man, or in any species of animal 

 that can live on a mixed diet, there is a variation of temperature 

 according to the mode of diet ; and it would be a good work to 

 inquire on a large scale if, under a purely vegetable form of dietary, 

 the temperature in man is reduced. Our correspondent informs 

 us that in him (a healthy man) and in his wife (a healthy woman), 

 both in the prime of life, the temperature now ranges from 96° to 

 to 97.4° F. He for three years and a half, and she for two years 

 and a half, have been total abstainers from alcohol, and have sub- 

 sisted on fruit and vegetables, with addition of " butter, cheese, 

 milk, eggs, and a little fish." Previously to adopting this system 

 his temperature had never fallen under 98° "in so far as he re- 

 members," and he therefore is inclined to the view that under his 

 new regime he lives as healthily as before, at a lower expenditure 

 of energy. If such prove to be correct, and if it should be demon- 

 strated that a minimum animal diet (for our correspondent, be it 

 observed, is not strictly a vegetarian) will support life efficiently 

 under reduced combustion and reduced waste of material, a valua- 

 ble as well as curious fact will be added to our practical knowl- 

 edge. Evidently there is here open a fine field for a patient, per- 

 fectly unbiased, and truthful investigator. 



EVOLUTION.' 



In the course of that theory of natural science best known to the 

 outer world as that of evolution or development (whereof Darwin 

 was the principal expounder), it becomes necessary for the theo- 

 rist to endeavor to bridge over the gaps which are very easily to 

 be discerned betwixt existing classes of animals. No doubt geol- 

 ogy has supplied not a few of those " missing links," and has un- 

 doubtedly proved, for example, how the modern one-toed horse 

 has descended from a four or five toed ancestor; and how birds 

 and reptiles, which every zoologist knows are near kindred, can 

 be linked by at least one fossil bird, which is neither bird nor rep- 

 tile, but a very decided mixture of both groups. Still, the geo- 

 logical record is an imperfect one, and always will be. If every 

 living thing which had ever existed had been preserved in a fossil 

 state, and had been placed at the disposal of the geologist and 

 anatomist for investigation, there might have been few or no diffi- 

 culties in the way of piecing together the bits of the puzzle of 

 life. As, however, fossil animals and plants constitute the mere 

 chance preservations of the life that was, we have perforce to be 

 content with a very meagre knowledge of existence in the past 

 ages. 



There remains, however, another method of arriving at the re- 

 lationship which science seeks to show exists between apparently 

 diverse groups of animals and plants. In plain language, when 

 we study the development of an animal or a plant, and see how it 

 works its way from the germ to become the adult form, we are 

 brought face to face with a series of changes and scenes which are 

 significant enough to the thinking mind. Suppose we discover 

 that a frog begins life as a fish, a fact every schoolboy knows, 

 what is the meaning of this strange becoming on the part of that 

 tailless animal? Natural history replies that the frog's develop- 

 ment we see to-day is really a recapitulation of its past descent. 

 ' Dr. Andrew Wilson, in the Illustrated l«ews of the World. 



Witnessing how a tadpole becomes a frog, we are really looking 

 at a moving panorama of the rise and progress of the whole frog- 

 race, whereby that race must have sprung from a fish-like stock, 

 and must have gradually grown into the lung-possessing, air- 

 breathing creatures of the present time. This seems to be the 

 only reasonable interpretation to be placed upon the marvellous 

 changes which we see represented in the development of animals 

 and plants; and this, at least, is the meaning which science at- 

 taches to the unfoldings of form and structure discernible in the 

 course of the living being's progress from its beginning, in the 

 egg, to its assumption of its adult character. 



In the course of studies in the development of animals, we 

 meet with some veiy curious discoveries and theories relative to 

 the origin of the various zoological groups; and certain ideas of the 

 origin of backboned animals at large, lately promulgated, seem to 

 be worthy of mention here, as tending to keep us au courant with 

 the progress of thought in biology. The puzzle of naturalists has 

 been that of accounting for the origin of the vertebrated animals 

 aforesaid, because these backboned tribes (which range from the 

 fishes to quadrupeds) seem really to stand out very distinctly and 

 by themselves as a specially defined sub-kingdom. The backboned 

 branch of the animal tree, in other words, has presented great 

 difficulties in its being traced to its connection with the parent 

 stem. There is a certain fish, the lowest of its class, called the 

 lancelet, which is found to present, both in its development and 

 in its adult structure, certain close affinities to a lowly tribe of 

 creatures known as tunicates, or sea-squirts. A sea-squirt is sim- 

 ply a kind of animated bag with two openings, somewhat like an 

 ancient "leather bottel," which remains attached to a rock or 

 stone. Hence, from the likeness between the sea-squirt's develop- 

 ment and that of the lowest fish, many zoologists are given to re- 

 gard the former as the putative parent of the vertebrate animals. 

 The sea-squirt, in this view, is the very far-back ancestor (or repre- 

 sentative of the ancestor) of the backboned tribes. 



More recently, however, certain adventurous spirits in biology 

 have ventilated new ideas of the origin of the backboned forms, 

 and these ideas, I fancy, are more startling even to biological 

 minds (given to feel surprised at nothing whatever) than any 

 previous theories which have been advanced. Seeking for the 

 ancestors of backboned animals among the annelids or worms has 

 not been a process attended by success, in so far as evidence of 

 probability is concerned; but higher in the series of jointed or 

 articulate animals we find the insects, spiders, and crustaceans, of 

 which class the lobster is a fair representative. One scientist de- 

 clared that for choice he finds the most likely origin of the back- 

 boned tribes in the spider-class. What induces this belief is the 

 tendency to head development, among other signs of advance, 

 which the spiders, scorpions, and their allies exhibit. What we 

 call a scorpion's head is really its head and chest united, and a 

 close examination of this region shows that in the arrangement of 

 its nerve-masses, its nerves, sense-organs, and so forth, there is to 

 be traced a very exact resemblance to the similar arrangements in 

 the vertebrate head. Again, it is held that in the development of 

 the scorpion and spider, essentially similar features to those seen 

 in backboned development are to be traced. So that the far-back 

 ancestor of the highest animals, on this belief, are to be sought for 

 in some primitive scorpion, which, getting on in the world, gave 

 origin to the higher group. There might be a difficulty regarding 

 the transition from air to water, from scorpion to fish, no doubt ; 

 but I presume it is maintained that out of a common type of primi- 

 tive breathing organ the modification in question could easily have 

 occurred. 



The other theory of vertebrate origin also sees the ancestor of 

 backboned animals in some primitive jointed animal or other. 

 Tracing the development of the backboned brain and spinal cord, 

 an observer regards these important structures as having been 

 formed by the elaboration of jointed nerve-masses placed on the 

 outside of a tube. There is such a tube in the middle of the spinal 

 cord, and this tube extends onwards into the brain. The bold idea 

 has therefore been formulated that the central nervous canal of 

 the backboned tribesrepresents the digestive tube of the vertebrate 

 ancestor; certain dilatations of the tube in the brain corresponding 

 to the stomach of that ancestor, whose own nervous system (lying 



