150 



NATURE 



[October 23, 1919 



of much value in reference to origins, but there 

 is some utility in thinking of the numbers of types 

 in the two habitats, and of cases where the enor- 

 mous majority of the types in a phylum are in the 

 one or the other. Now, if we begin with the 

 lowest phyla of Metazoa, the Sponges and 

 Ccelentera, we find in both cases the vast majority 

 of types in the sea and a very small minority in 

 fresh water. The most natural — though not in- 

 evitable — inference is that the present-day habitat 

 of the vast majority is the original habitat. The 

 Echinoderms represent a well-defined phylum, all 

 the living representatives of which are marine. 

 The types at the base of the Chordate phylum — 

 namely, Enteropneusts, Tunicates, and Lancelets 

 — are all marine, which is again significant. Many 

 similar cases might be given, but Prof. 

 Macfarlane advances counter cases, and actual 

 demonstration is out of the question. 



(fc) If we take a number of notable advances, 

 such as paired unjointed limbs or parapodia, such 

 as body-segments or metameres, such as genuine 

 pre-oral appendages, such as the annulate or the 

 chordate type of nervous system, such as true gill- 

 clefts, such as a dorsal axis, and ask where they 

 began, the evidence from present-day forms and 

 from palaeontology is on the whole in favour of the 

 answer : In the sea. But Prof. Macfarlane brings 

 forward counter instances, and no doubt the fresh 

 waters have been a very educative school of life. 



(c) Types with direct life-histories are very 

 generally, though not always, less primitive than 

 related types with larval stages, and the tendency 

 of fresh-water animals to have little in the way of 

 larval stages (telescoping these, according to our 

 theory) is very striking except along a few lines, 

 such as that of aquatic insects, which are no doubt 

 primarily terrestrial. And it is not difficult to see 

 why it should be so. 



{£) For most of the types of fresh-water animals 

 it is possible to give a plausible pedigree, starting 

 from marine or terrestrial forms. 



(e) It is a significant fact, emphasised by 

 Quinton, that the blood of land animals", 

 such as mammals, is in the proportion of sodium, 

 potassium, and calcium ions almost identical with 

 sea-water. It is diflficult to interpret this except 

 as a hint of pedigree. 



(4) It is impossible to do justice in a few lines 

 to Prof. Macfarlane's long discussion of the phylo- 

 geny of animals. He regards Rotifers — in spite 

 of the specialisation of most of them — as "the 

 foundational group " of the simpler Metazoa, and 

 he has the hardihood to place a ciliated Infusorian 

 and a Rotifer side by side, for "the lines of 

 stereogenesis in the Rotifera remain fundamentally 

 as in cifiate Infusoria." We do not profess to 

 know much about stereogenesis, but the juxta- 

 position of a Rotifer not only with an Infusorian, 

 but also with a larval Entomostracan and a larval 

 Gastropod strains our morphological faith. It 

 must be a foundational creature indeed which is 

 like three things so different. The author traces 

 the main line of ascent from the Rotifers through 

 NO. 2608, VOL. 104] 



Turbellarians, Nemerteans, Cyclostomes, Ca'cili- 

 ans, to Marsupials and higher Mammals. The 

 difficulties involved in side-tracking Tunicates and 

 Lancelets and in dragging Cyclostomes and 

 Caecilians on to the direct line of ascent seem to 

 us to be insurmountable. But this is largely a 

 matter of opinion. It seems to be truer of phylo- 

 geny than of statistics that if you pick your data 

 you can prove anything you like. There are, 

 naturally enough, some loose ends in Prof. 

 Macfarlane's arguments. These are of two kinds 

 — matters of fact, as when he says that the eggs 

 , of Cyclostomata undergo holoblastic segmenta- 

 tion, which is not true of Myxinoids ; and matters 

 of interpretation, as when he says of the Caecili- 

 ans : " the active gliding habits and slippery skin, 

 also, scarcely serve to set up the needed irritable 

 stimuli that would start paired limbs as a 

 response-result." This surely verges on the 

 poetical. 



(5) A useful chapter on " higher " animals ex- 

 pounds the not unfamiliar idea that along different 

 lines and at different structural levels animals rise 

 to approximately equal complexity of behaviour. 

 Thus octopus, spider, ant, crow, and elephant are 

 types that rise high along different lines of struc- 

 tural advance. This is sound enough, though it 

 is time that Sir Ray Lankester's distinction 

 between the "little brain " and the "big brain " 

 types of cleverness was recognised in all such com- 

 parisons, but what seems to us quite in the air is 

 Prof. Macfarlane's theory that the "energising 

 stimuli " of a complexified environment excite the 

 biotic system of the body and the cogitic cells of 

 the brain to new adjustments and adaptive 

 changes, " all of which are more or less shared by 

 and influence the generative cells, which in turn 

 affect the succeeding organisms hereditarily." In 

 other words, without any submission of* evidence, 

 we are asked to return to the credulity of 

 Lamarckism. The author says : " To repeat once 

 more our fundamental position : flows of energy, 

 often and steadily repeated from sense-collecting 

 centres, start stereo-energetic stimulation-acts, 

 that inevitably affect the brain-cells, and these by 

 expenditure of cogitic energy give rise to pro- 

 environal responses that constantlv tend to place 

 the organism for the time being in ' satisfied ' 

 relations to its environment." In so saying he 

 seems to us to be stating with unnecessary tech- 

 nicality the fact that living creatures adjust them- 

 selves within limits to their surroundings ; but 

 when he suggests that the elephant's trunk 

 evolved by the transmission of the results of in- 

 dividual "proenvironal reponses," we feel bound 

 to say "napoo." 



(6) In regard to the .Ascent of Man, the author 

 lays emphasis (as .\nthonv, Wood Jones, and 

 others have done) on the evolutionary importance 

 of the emancipation of the hand which " stimu- 

 lated the brain to increased flows of energy and 

 so increased complexity and growth." "In all 

 such advance by environal stimulat'on-action and 



i brain reaction, followed by proenvironal outreach- 



