44 Dr Gaskell, The Origin of Vertebrates. [Dec. 2, 



It is clear that the study of the ccelomic cavities in the head 

 not only gives no support to the opponents of my theory but like 

 the corresponding argument of the hippocampus minor affords yet 

 another extraordinary coincidence, so that I presume that the 

 resemblances between the head cavities of the Vertebrate and of 

 Limulus must now be included among the rest of the trivial 

 coincidences. 



Before leaving the consideration of the ccelom, I must say that 

 I heard to my utter astonishment the statement of both Mr 

 Macbride and Mr Shipley that my theory was preposterous, 

 because I made the generative and excretory organs of the 

 Vertebrate arise de novo. Seeing that I have not said a word 

 about the origin of the excretory and generative organs of Verte- 

 brates and have never even dreamt of making them arise de novo, I 

 cannot understand how such an argument can be used against me. 

 It is true that I believe that the pituitary gland is simply the 

 coxal glands of Limulus and Scorpions, but that does not imply, as 

 Mr Shipley asserts, that the renal organs of the Arachnoid ancestor 

 degenerate into the pituitary body ; for undoubtedly Scorpions 

 and other Arachnids possess a well-defined renal system known by 

 the name of the Malpighian tubes. 



Then I am told that the Arthropod does not possess a noto- 

 chord, while the notochord is the great characteristic of the 

 Vertebrate ; and I am asked, Where is the notochord in Limulus ? 

 Similarly in the old controversy it was asked, Where is the 

 opponens pollicis in the ape ? Just as in the latter case the 

 opponens pollicis is an attribute of man because he has discarded 

 the quadripedal method of progression and become a biped, so the 

 notochord is an attribute of the Vertebrate because it has dis- 

 carded the old alimentary canal and formed a new one. I had not 

 intended to discuss the origin of the notochord at present, but as 

 stress has been laid upon its presence and I have been challenged, 

 I will simply ask the following questions : — "Do embryologists 

 consider that the notochord arose as a simple tube of hypoblast 

 which terminated in the region of the infundibulum and extended 

 the whole length of the body?" If so, "Is it possible to conceive 

 of more than one interpretation of the original purpose of an un- 

 segmented hypoblastic tube in a segmented animal which extends 

 the length of the body from mouth to anus?" I will also point out 

 that just as the notochord is formed by the proliferation of cells in 

 the median line ventral to the nervous system, so later on in the 

 history of the animal a similar proliferation of cells takes place in 

 the same region to form the sub-notochordal rod ; and again when 

 the Ammoccetes transforms into the Petromyzon, yet another 

 similar proliferation takes place in exactly the same region, but 

 now confined to the ancient part of the animal, viz. the head 



