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NATURE 



[May 20, 1922 



phenomena. However convenient for practical pur- 

 poses a separate department of biochemistry may be, 

 it would be a matter for regret if this part of physiology 

 became dissociated from the remainder. Indeed, it 

 may safely be said that no physiological laboratory 

 can carry on effectively any part of its work without 

 the provision of a chemical department. Hence, bio- 

 chemistry, as well as biophysics, must be included. 

 What is needed seems to be the establishment of more 

 chairs in what might properly be called " general " 

 physiology, as distinct from " special " or human 

 physiology. Since the term " general physiology " is 

 sometimes misunderstood, and limited to the lower 

 animals, perhaps the title of " biodynamics," sug- 

 gested by the writer in another place, might be more 

 appropriate. This name distinguishes the science of 

 function from that of structure. Although, of course, 

 one carmot exist apart from the other, such a separa- 

 tion is more scientific than that of the chemical from 

 the physical departments of physiology, for the methods 

 of both the fundamental sciences are needed for the 

 proper investigation of vital problems. 



At the same time, there may be said to be a more 

 purely chemical branch of biochemistry, that devoted 

 to the study of the properties of various compounds 

 prepared from or by the hving organism. This is 

 really a special part of organic chemistry, and is 

 obviously more related to the science of structure 

 than to that of function, although it may conveniently 

 be studied in connection with physiology. There is, 

 however, an unfortunate tendency to call a man a 

 " biochemist " who may be devoid of any acquaintance 

 with vital phenomena. Another tendency, also apt 

 to lead to confusion, is that of including pathological 

 chemistry under biochemistry. This should surely be 

 the chemical side of pathology, dealing with disease 

 as physiology deals with normal processes. These 

 remarks are not in any way intended to undervalue 

 the pursuit of biochemistry, but as an attempt to 

 make its position clear. Prof. Moore's book takes into 

 consideration more than the chemistry of vital pro- 

 cesses, so that the title is not altogether an appropriate 

 one. W. M. B. 



Morphological Aberration. 



The Echinoderms as aberrant Arthropods. By Austin 

 H. Clark. Smithsonian Miscellaneous Collections, 

 vol. 72, No. II. Pp. 20. (Washington, July 20, 

 1921.) 



FOR some years past Mr. Austin Hobart Clark 

 has been flirting with the idea that the Echino- 

 derms were derived from the Arthropods, but we all 

 NO. 2742, VOL. 109] 



pretended not to notice. Now that he has come into 

 the open with a paper published by no less a body 

 than the Smithsonian Institution, and that he has 

 sent us a copy for review, we are obliged to reprobate 

 such goings-on. 



What Mr. Clark suggests is not merely such connec- 

 tion of the Echinoderma with the Arthropoda as others 

 find with the Protochordata ; he is " convinced that 

 they are undoubtedly closely allied to the crustaceans, 

 and especially to the barnacles." No one can have 

 failed to remark some resemblances between crinoids 

 and cirripedes, due to a somewhat similar mode of 

 life : normally both are attached — whether by a stem 

 or immediately sessile ; the body is encased in plates, 

 and from it project jointed and often branched ap- 

 pendages used for collecting food. It is not easy 

 to gather precisely how much importance Mr. Clark 

 attaches to these and other adaptive resemblances : 

 we may give him credit for the statement that " there 

 can be no question of any direct homology between " 

 them, and confine him to the suggestion " that it is 

 not impossible to regard them as parallel manifesta- 

 tions of the same ancestral appendicular plan." The 

 trouble is that he will keep dragging in, not merely 

 the highly specialised sub-class Cirripedia, but the 

 most modified forms of that sub-class, thus : — " A 

 combination of the asymmetry of the Verrucidae [a 

 geologically late family of cirripedes] (inherent also 

 in very many other crustaceans, and especially notice- 

 able in the Paguridae and Bopyridse [hermit-crabs 

 and parasitic isopods]) carried to its logical conclusion 

 in the complete atrophy of one side, with the modifica- 

 tions of the body seen in Sphserothylacus or Sarcotaces 

 [problematic parasites] in a less extreme form, the 

 roots of the Rhizocephala [parasitic cirripedes], and 

 a skeleton formed after the manner of the plates in 

 the shell of the Operculata [sessile barnacles of late 

 origin], furnishes all the elements needed for recombina- 

 tion to form the crinoid." It is fairer to Mr. Clark to 

 ignore these and similar comparisons of incomparables, 

 and to consider only the fundamental parts of his 

 argument. 



The " outstanding features " of the echinoderms 

 are, says Mr. Clark, " the presence of a vascular, a 

 respiratory, and a superficial skeletal system, the last 

 composed of articulated (calcareous) elements, the 

 absence of gill clefts, and the sharp division of the 

 body externally into (five radial) segments. In these 

 features they agree only with the arthropods." Prob- 

 ably he means : " In the combination of these features." 

 But, take the characters singly, and what is the 

 resemblance } The so-called vascular system of 

 echinoderms is most feebly developed and possesses 

 no heart or other means of causing its contents to 



