WHAT IS MORPHOLOGY? 



359 



the noble vertebrata. The noisiest claimants are 

 the worm and the ascidian — that poor relation of 

 the oyster ; by some this is thought to be mad- 

 ness, but there is method in it. I will now quote 

 part of an article which appeared in the Nine- 

 teenth Century for December last, on " Recent 

 Science." The writer is giving an account of Prof. 

 Reichenbach's beautiful researches into the em- 

 bryology of the common fresh-water crawfish, and 

 then he goes on to compare the development of 

 the nervous axis both in the invertebrata and ver- 

 tebrata : 



" Until quite recently the manner in which the 

 central nervous system arises has always been 

 considered as one of the most important distinc- 

 tions between vertebrate and invertebrate ani- 

 mals. In the former, at the period when the em- 

 bryo is a small three-layered patch on the surface 

 of the egg, a longitudinal groove appears, the side- 

 walls of which, meeting above, inclose a tube lined 

 by the epiblast. From the epiblastic cells thus 

 shut off, the whole brain and spinal cord are pro- 

 duced, together with the roots of the cranial and 

 spinal nerves, as the recent observations of Mr. 

 Balfour ' and Dr. Marshall J have shown. In the 

 invertebrata, on the other hand, it was always 

 supposed that the nerve-cord was produced from 

 the middle layer of the embryo, or mcsoblast ; 

 but this has been shown not to be the case, for it 

 has now been proved that, in many of these, the 

 nervous system arises from a thickening of epi- 

 blast, which only differs from the corresponding 

 structure iu vertebrata by the fact that it is not 

 sunk in a groove. But the relation, in this re- 

 spect, of the two great groups of the animal 

 kingdom has never been more clearly brought out 

 than in Reichenbach's 3 paper. He shows not only 

 that the nerve-cord is a product of the epiblast, 

 but that it arises from the cells lining an actual 

 groove — a groove having precisely the same rela- 

 tions, and in one part of its course being nearly 

 as deep, as the ' medullary groove ' of a chick 

 or a tadpole. He also shows that the eyes are 

 formed not, as is usually stated, as elevations, but 

 as depressions in the epiblast ; the cells lining 

 these depressions becoming connected with those 

 of the first ganglion of the nerve-cord. Here, 

 again is a remarkable resemblance to vertebrates, 

 in which the organs of the higher senses always 



1 "On the Development of the Fresh-water Craw- 

 fish." (" Die Embryonanlage und erste Entwickelan? 

 dcs Flusskrebses.") Zeitschr?ftfurwi$s.Zool.,xx\x. 

 Bd. 2. Heft, July, 1877. 



2 " Philosophical Transactions," vol. clxvi., and 

 Journal of Anatomy and Physiology, April, 1877. 



s Journal of Anatomy and Physiology, April, 1877. 



originate as involutionsof the surface-layer " (page 

 896). 



I have thus passed insensibly from the mean- 

 ing to the aims of morphology. I trust you will 

 agree with me, that it is "a topmost fruitful 

 bough" of the great tree of modern science; it 

 is certainly fuller of buds than of flowers, for now 

 is its early spring only. Kindly attend while I 

 open a bud or two to show you what the flowers 

 promise to be. 



The ends and aims of morphology are differ- 

 ent from those of physiology ; histology may be 

 said to be equally related to each and ancillary 

 to both. The study of one branch seems to ask 

 in its workers for an innate fitness for the one 

 rather than for the other. One man sharply 

 questions the why of Nature ; the other patiently 

 searches after the how. Morphology asks for 

 One who can work and wait in silence year after 

 year ; and his qualities have need to be those of 

 quick insight, combined with the most phlegmatic 

 laboriousness. Here, in this case, natural quali- 

 fications are of more importance than those which 

 can be acquired. But the physiologist sharply 

 asking why needs to be trained for his work ; he 

 must be a mathematician and a chemist as well 

 as an anatomist ; ready action and cunning inven- 

 tiveness are most needed in him ; a seeing eye, a 

 copying hand, and a somewhat imaginative na- 

 ture — these are the qualifications asked for in 

 the morphologist. Delight in living forms and 

 their transformations shows itself very early in us 

 all ; morphology is aesthetic before it is scientific ; 

 it becomes scientific as soon as it is comparative. 

 The morphologist is nothing if not comparative ; 

 the development of accurate observation, com- 

 bined with ready and constant comparison and 

 unconscious classification — these are the neces- 

 sary elements in the morphological worker. 



The group of animals to which we belong-^- 

 the vertebrata — considered as to their skeletal 

 morphology, form alone a wide field ; " there is 

 yet much land to be possessed." In that division 

 of a subdivided science I have chosen for time 

 and for work's sake mainly the head ; for in it 

 are to be found the most intricate interweavings, 

 the hardest knots of Nature. For a time, for 

 work's sake, one kind of head is enough ; if all 

 the parts are to be considered in their origin and 

 relations, in their changes and development. For 

 the solid and supporting parts of the building, so 

 to speak, are to no purpose, have no meaning, if 

 we could possibly forget their contents and their 

 outgoing and overlying parts. 



Considering the great complexity of structure 



