126 PROCEEDINGS OF SOCIETIES. 



Royal College of Surgeons, Hunterian Lectures on the 

 Invertebrata. By Prof. T. H. Huxley, F.R.S. (Abstract.) 



Lecture I. — Having treated of the vertebrata in previous 

 courses, there remained for consideration the rest of the 

 animal kingdom known as Invertebrata. Professor Huxley 

 remarked that the line between Vertebrata and Invertebrata 

 was very definite. There are no links leading in any way 

 from any of the great groups of Invertebrata to the Verte- 

 brata. It must not, however, be supposed that the Inver- 

 tebrata are equivalent as a group to the ^"ertebrata : they 

 are a much larger and more various assemblage. The Inver- 

 tebrata cannot be limited so sharply at the other end of the 

 scale, viz., where they approach plants. The higher plants 

 are very broadly distinguished from the higher animals. 

 Plant-cells (using the term " cell " without prejudice) are 

 surrounded by cellulose — a non-nitrogenous substance. No 

 animal cell ever presents this. By this prison- wall of cellu- 

 lose, all undoubted plants are prevented from exhibiting 

 locomotive processes. For the same reason no plant takes 

 solid nutriment. All the higher plants are manufacturers : 

 they have the wonderful power of uniting carbonic acid, 

 water, and ammonia, to form protein compounds. Plants 

 alone are known to possess this power of making " vital 

 matter." All animals on the other hand (omitting the 

 debateable organisms) exhibit the reverse action of breaking 

 down and using up this vital matter. But when we come to 

 the lowest forms of life, these tests of animality and vege- 

 tability fail us. Cienkowski has recently shown that those 

 well-known forms called monads lose their ciliuni and become 

 amoebiform, taking in solid nutriment like undoubted animals. 

 But soon they become enclosed in a cyst of cellulose (by its 

 reactions), and become coloured with chlorophyl. In this 

 stage they are no less undeniably plants. The mass enclosed 

 in the cyst breaks up into four or more pieces, which in due 

 time become again the animal -like monad. This case and 

 many similar examples have led many naturalists to abandon 

 altogether the attempt to make a sharp line between plants 

 and animals. Not only do the morphological tests fail, but also 

 the physiological ; for many fungi we know require to be fed 

 on organic materials. Professor Huxley believes that opinion 

 has long been tending to this, that Man and the magnolia 

 are but extreme terms of a continuous s.erics. This must by 

 no means be understood us implying development from a 

 common stock ; that is quite another question, and does not 

 afl'ect the facts. Other naturalists have proposed a group of 

 neither plants nor animals — a sort of " no-mau's land " to 



