602 MORPHOLOCJICAL METHOD AND RECENT PROGRESS IN ZOOLOGY. 



shield- lunirino- Ushcs of the Devonian and Sihirian epoeh.s, and that 

 through them the}^ are ancestral to the Vertebrata. The latest phase 

 of this idea is based on the supposed existence in a Ce}>h<tJ(ix}>ix of a 

 series of twenty-live to thirt}' lateral appendages of arthropod type. 

 When, however, it is found that the would-be limbs are ])ut the edg-es 

 of body scutes misinterpreted, suspicion is aroused; and when, work- 

 ing back from this, an earlier attempt reveals the fact that the author, 

 compelled to lind trabecular, in order to force a presupposed compari- 

 son between the architecture of the Cephalaspidian head shield and 

 the Linuilus' prosonial hood, resorts to a comparison l^etween the 

 structure of the former in general and that of the cornu of the latter, 

 with details which on the piscine side are not to date, the argument 

 iimst be condemned. It violates the tirst principles of comparative 

 morphology, and is revolting to connnon sense; and as to the lishes 

 concerned, we know that they have nothing Avhatever to do with the 

 Linudoids, for we have already seen that, with their allies the Pteras- 

 pidia;, they are a lateral l)ranch of the ancestral piscine stem. 



The second advance upon the King crabs has very nuich in common 

 with the tirst. It has engrossed the attention of an eminent physiolo- 

 gist for the last six or seven 3'ears, and by him it was in detail set 

 before Section I at our meeting of 18iM). Suffice it to say that it specially 

 aims at estal)lishing a structural conmuuiity between the king cral)s 

 and certain vertebrates, favorable to the conviction that the vertebrata 

 have had an arthropod ancestry. When we critically sui'vey the 

 appalling accumulation of words l)egotten of this task, it is sufficient 

 to consider its opening and closing phases. At the outset, under the 

 conclusion that the vertebrate nervous axis is the metanior2)hosed 

 alimentary canal of the arthropod ancestor, the necessity for tinding 

 a digestive gland is mainly met by homologizing the so-call(^d li\ er of 

 the arthropod with the cellular arachnoid of the larval lamprey, in 

 violation of the first principles of comparative histology. \i the close 

 we find ingenious attempts to homologize nerve tracts and commissures 

 related to the organs of sense, such as are invariably present wherever 

 such organs occur. Sufficient this to show that the coujparison, in 

 respect to its leading features, is in the opening case strained to an 

 unnatui'al degree, in the closing case no comparison at all. Finding, 

 as we do, tiiat the rest of the work is on a pai' with this, \v(» are com- 

 pelled to reject the main conclusion as unnatural and unsound; and 

 when we seek the explanation of this rcmarka])le cours(> of action, we 

 are forced tobeliev(> that it lies in the failure to unchu'staiid the nature 

 of the m<)i[)hol()gi('al method. For the projx'r pursuit of comparative 

 in()i))li()l()gy, it is not sulficient that any two organisms chosen here 

 and there should b(> compared, with total disregard of (>v(mi elementary 

 })rincii)les. Comparison should be first close and with neaily iclated 

 foinis, passing later into larg(>r groups, with the progressive 



