Royal Microscopical Society. 99 



microscope ; and to him, to anyone indeed, who adds a single fact 

 to the science of life. It has been cast at ns, as Fellows of this 

 Society, that we do nothing but improve our tools, or measure the 

 markings on the frustule of a diatom, or count the bristles on a 

 flea's nose. We need care but little for these criticisms; whatever 

 we have done, if so be it has been done well, will have a recognized 

 and permanent value. However, it is possible and even desirable 

 that we should improve ; and this one thing we will do, and our 

 monthly journal shall witness for us that we have not been fag- 

 goted together into a society in vain. I am afraid you are saying 

 this is a long introduction ; it is ; but the discourse shall be short. 

 My proper duty for this evening was not to go rambling over all 

 creation, " rounding about," as Bacon would have said, but to ask 

 your attention to some plain details concerning my own work. This 

 work is on one special subject, viz. the formation of the skull and 

 face of one of the ordinary mammalia. It was my purpose to have 

 taken the guinea-pig as a fresh subject of research, but I was led 

 to change it through the kindness of my friend Mr. Charles Stewart, 

 who put into my hands about seventy embryos of the common pig. 

 These are of six or seven different stages, and range from the 

 size of a bee's grub to that of a new-born kitten. I have supple- 

 mented these by specimens of the sucking-pig, and the carefully 

 prepared skull of one that died in an emaciated condition at six 

 months old. This specimen, being absolutely free from fat, is as 

 pleasant an object as if it were composed of ivory. For my work, 

 as many young elephants and hippopotamuses, or even hairy 

 rhinoceroses, would not have served my purpose better than these 

 germinal pigs. Indeed, I very much question if a more central 

 type could be found. It is commonly believed that the pig comes 

 very near to man in its internal structure ; happily for us, zoology 

 places it very far from our group. Yet, when my plates are 

 finished, they will show the marvellous conformity between the 

 highest and the medium type of the mammalia. I am satisfied that 

 all those who are not in the secret will suspect me of having 

 laboured at the primordial form of my own species. The size of 

 the smallest of these embryos is ^ths of an inch in length, then 

 an inch, then an inch and a third, and so on. But the complete 

 bony framework of the skull and face is best seen in the 

 skull of the half-grown individual, where all the bones are well 

 developed, but are, to a large extent, distinct from each other ; in 

 old individuals, they are largely coalesced. The higher types of 

 vertebrated animals undergo as real a transformation as the lower, 

 such as the newt and the frog ; so that we do not watch merely the 

 expansion of the parts, but also their metamorphic changes. This 

 metamorphosis is exactly like what is seen in the lower forms, but 

 it runs to a higher pitch, and takes place more rapidly ; whilst 



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