188 PEOF. JOHN CLELAND^ M.D., ETC., ON 



time on the Invertebrata than the Vertebrata, but still, as an 

 anatomist, I feel raiTch interested in the question that has been 

 so ably brought up. I think there still remains great doubt about 

 the internal evidence of evolution apart from a superintending 

 cause in which skill and design have. been most clearly carried 

 out, and no question of environment or any other condition of life 

 in connection with the survival of the fittest will explain evolution. 

 It has been stated so in this paper. 



Though the mammal and the bird are very distinct in their 

 leading characteristics, the transitional forms are few and far 

 between : the Ornithorhyiichvs is, perhaps, the most striking 

 example. Again, in the passage from the reptile to the bii-d we 

 have the Ftprndactyle, and it is impossible to ignore the construc- 

 tion of the beak and fins of the turtle as exhibiting at least a 

 representative relationship to the corresponding parts of the 

 Penguin. 



The reptiles and fishes are singularly connected by the Lepido- 

 Riren, and it is usual to trace fishes fi-om the Aiiipliio.rufi lanceolatuf; 

 and the latter from the Tunicafa, to the exclusion of the Molhisca 

 proper, so that whatever had been gained or achieved by Nature 

 in the magnificent eye of the Cuttlefish does not appear to be 

 turned to account in the Amph! oxn.fi, which has either no eye at all 

 or a rudimentary eye speck. 



A good lesson may be derived from tlie study of the develop- 

 ment of the circulatory system, which is so much consulted in 

 reference to classification. It is at first purely ciliary (Livgvla), 

 and the outgoing and returning currents course along opposite 

 sides of the same vessels. Secondly, without any valvular 

 mechanism the whole round of the circulation in the Tunicafe 

 sweeps alternately in opposite directions. Thirdly, in the true 

 Mollusca the supply of valves determines an irreversible course 

 to the circulation, and the whole organization is as perfect as we 

 find it in any fish. 



Finally, with gills or lungs the circulation is either branchial or 

 pulmonic as well as systemic. 



J. W. Slatek, Esq., F.E.S., F.C.S. — I have presumed to put down 

 afewof my own i^emarks as comments on Professor Cleland's address, 

 which may not, perhaps, be without interest at the present junc- 

 ture. Those who, like myself, have had the advantage of studying 

 Professor Cleland's thoughtful and .suggestive paper on " Terminal 

 forms of Life " will be exceptionally in a position to appi'eciate 

 the paper with which we have just been favoured. It is plain 



