436 Mr. T. H. Huxley on the genus Thalassicolla. 



of an inch in diameter (4 e). Some of these had a sohd greenish 

 red nucleus about yjo o^^ °^ ^^ ^^^^ i^ diameter. Others re- 

 sembled the nuclei in colour and appearance, but were larger 

 (2 j(j(yth of an inch), and had no cell-membrane : — were these 

 granule cells ? 



Altogether the Thalassicolla nucleata might readily be imagined 

 to be a much-enlarged condition of single cells of the Th. punc- 

 tata ; but I have no observations to show that it was so, nor can 

 it be said from which of the varieties of Th. jmnctata the Th. nu- 

 cleata arises. 



The question may readily arise, Are these perfect forms ? I can 

 only say, as negative evidence, that I have never observed any 

 trace of their further development, and that the spicula and 

 * shells,' and the capacity of fission, appear to afford positive 

 grounds for believing that they are not mere transitional stages 

 of any more highly organized animal. If, further, it can be shown 

 that their structure is closely allied to that of known organisms, 

 this probability will, I think, almost amount to a certainty. 



What animals are there then which consist either of simple 

 cells or of cells aggregated together, which hold the same rank 

 among animals that the Diatomacese and Desmidise, the Protococci 

 and Palmellse hold among plants ? 



Ten years ago the general reply of zoologists would have been 

 — none. The researches of the celebrated Berlin microscopist. 

 Prof. Ehrenberg (wonderful monuments of intense and unremit- 

 ting labour, but at least as wonderful illustrations of what zoo- 

 logical and physiological reasoning should not be), led to the be- 

 lief that the minutest monads had an organization as complicated 

 as that of a worm or a snail. In spite, however, of the great 

 weight of Prof. Ehrenberg's authority, dissentient whispers very 

 early made themselves heard, from Dijjardin, Focke, Meyen, 

 Rymer Jones, and Siebold. To these Kolliker, Stein and others 

 — in fact, I think I may say all the later observers — have added 

 themselves, until it really becomes a matter of duty on the part 

 of those interested in the progress of zoology to pronounce de- 

 cidedly against the statements contained in the ' Infusionsthier- 

 chen,' so far as regards anatomical or physiological facts*. 



It has been shown in the first place, that a great mass of the 

 so-called Polygastria are plants — at any rate are more nearly allied 

 to the vegetable than to the animal kingdom. Such is the case 



* That the above assertions will be considered by the majority of En- 

 glish readers to be unwarrantably severe, and considering the relative 

 standing of the Professor and his critic, possibly impertinent, is no more 

 than is to be expected. 



I can only beg to disclaim all mere iconoclastic tendencies, and refer to 

 a comparison of Prof. Ehrenberg's works with facts for my justification. 



