58 Prof. C. Clans on the 



Altliongli in accordance witli my own comparison (published 

 in 1876) I cannot see why the pectinate appendages cannot 

 represent the second pair of limbs, I nevertheless entirely 

 agree with Packard in regarding the attempt to refer the 

 lung-sacs of the Scorpion to the introverted branchial laminje 

 of the last four pairs of limbs, as mere trifling with baseless 

 assumptions. In point of fact this exceedingly remarkable 

 speculation (which its author has, however, replaced by a new 

 one) furnishes us with a not very edifying example of the 

 ingenious hypotheses into which an unbridled imagination may 

 lead the morphologist. 



It fares no better with the assertions as to the agreement 

 between the brain, nervous system, and eyes in the two types. 

 Packard shows Lankester to be in error when he shifts the 

 origin of the pair of nerves which run to the anterior extre- 

 mities in Scorpio^ from the brain, as in Limidus, to the 

 oesophageal ring ; and in the same way he disputes the inter- 

 pretation adopted by Ray Lankester to enable him to homo- 

 logize the scattered simple eyes of the Scorpion with the lateral 

 facetted eyes of Limulus. 



This, however, by no means exhausts the list of errors and 

 fallacies. Limulus^ like the Scorpion, possesses a supra- or 

 circum-medullary artery, which issues from the aorta and em- 

 braces the oesophagus. No Crustacean, says Pay Lankester, 

 has such a spinal vessel, consequently Limulus is an Arachnid. 

 But is our author so imperfectly acquainted with the anatomy 

 of the Crustacea as to have no knowledge of the vascular 

 system of the Isopoda, in which there is a peri-oesophageal 

 annular vessel, which issues from the aorta and receives blood 

 from it? In my work upon the organs of circulation in the 

 Schizopoda and Decapoda (Vienna, 1884) I have even at- 

 tempted to show the probability that this condition was perhaps 

 the original one in the ancestral forms of the Thoracostraca. 



And now as to the supposed perfect agreement in the form 

 and minute structure of the organs to which Ray Lankester 

 appeals as an argument for Liimdus being an Arachnid ! And 

 first of all the possession of reticulate sexual glands, which 

 are said not to exist in the Crustacea. Does not Pay Lankester 

 know the reticulate testes of the genus Ajjus, a genus which lie 

 made the subject of an extensive memoir ? And is he so little 

 able to judge of the morphological significance of a character 

 as to estimate, from a classificational point of view, the external 

 form of the sexual glands as a determinant factor in making 

 Limulus an Arachnid ? What have the comparisons of the 

 leg-glands (the so-called co.m?_5'?a«c/s), wliich are quite arbi- 

 trarily interpreted as segmental organs, to do with the proof 

 that Limulus is an Arachnid? or, lastly, the structure of the 

 so-called entochonflrites and inner skeletal structures in TAmu- 



