32 PKOCEEDINOS OP THE 



Prof. Authur Dbndy, F.R.S., Sec.L.S., contributed the follow- 

 ing remarks : — 



Any theory of the orii^in of Vertebrates must stand or fall by 

 the results of detailed criticism of the evidence upon which it 

 rests, and owing to the large amount of evidence which Dr. Gaskell 

 has brought forward, this must necessarily be a verv laborious 

 undertaking. The portion of this evidence to which I wish to 

 call special attention on this occasion is that which concerns the 

 eyes, upon which very great stress has been laid. This applies 

 especially to the median eyes, concerning which Dr. Gaskell 

 himself states * that " undoubtedly, in recent times, the most 

 important clue to the ancestry of Vertebrates has been given by 

 the discovery that the so-called pineal gland in the Vertebrate 

 brain is all that remains of a pair of median or pineal eves, the 

 existence of which is manifest in the earliest Vertebrates." This 

 being so, it seems especially desirable to examine criticallv the 

 evidence brought forward in this case. Dr. Gaskell has studied 

 these organs in the Ammocoete larva of Petromyzon. I myself 

 have studied them in the Velasia stage of the New Zealand 

 Lamprey, Geotria, which is very closely related to Petromyzon, and 

 also in Sphenodon, where they are exceptionally well developed. 

 I may say at once that my interpretation of their structure does 

 not agree with that of Dr. Gaskell. 



Dr. Gaskell reminds us that Crustaceans and Arachnids, as well 

 as A^ertebrates, have lateral and median eyes and that in these 

 Arthropods, " the median eyes are in all cases eves with a simple 

 upright retina and a simple cuticular lens, while the retina of the 

 lateral eyes is compound or may be inverted, according as the 

 animal in question possesses crustacean or arachnid aTfinities " 

 Again he says, " The lateral eye of the vertebrate, possessing, as 

 it does, an inverted compound retina, indicates that the verte- 

 brate arose from a stock which was neither arachnid nor crusta- 

 cean, but gave rise to both groups— in fact, was a member of the 

 great palaeostracan group."' He then proceeds to examine the 

 evidence with regard to the median eyes of Ammoccetes, with a 

 view to discovering whether they belong to the same type as 

 those of Arachnids and Crustacea. He compares an extremely 

 diagrainmatic figure of the pineal eye of Ammoccetes, which in 

 my opinion is far from being correct, with an apparentlv equally 

 diagrammatic figure of an Acilius larva, which, to judge "from the 

 drawing of this eye copied from Patten on a later page, is also 

 far from accurate. By this procrustean method of treatment 

 the two eyes are certainly made to look very like one another 

 although it has been impossible to eliminate the cuticular lens of 

 Acilius, which is entirely wanting in Ammoccetes. 



The manner in which it has been necessary to treat the evidence 

 in order to arrive at this comparison is clearly illustrated by 



* ' The Origin of Vertebrates ' : Longmans, Green, & Co., 1908, p. 74. 



