THE COASTS OF SICILY. 41 



physiologist Baer * developed analogous principles, 

 and since that date these researches have been con- 

 siderably multiplied ; and if we would here cite all 

 the authors who have furnished proofs in support of 

 this general fact, we should be compelled to give the 

 names of almost all modern embryologists. 



The most various researches, undertaken and con- 

 cluded by men whose doctrines often differ in respect 

 to many points, have nevertheless led to this one 

 general and identical result, that every germ in the 

 course of development is characterised from the 

 first as a vegetable or animal. In animals the pri- 

 mordial type is distinguished from the very earliest 

 time; next appear the characters essential to the 

 secondary types ; while, at a later stage, those of an 

 inferior zoological importance make their appearance, 

 and so on, until each part of the organism has 

 acquired the proportions, forms and colours, which 

 characterise the species. 



We thus see that the different phases of develop- 



* Baer, the author of a great number of works on zoology and 

 physiology, has connected his name with one of the most curious 

 discoveries of the present day. He was the first who saw and 

 studied the ovum of the Mammalia, hut in these observations, which 

 were made in 1827, he compared it to the germinative vesicle, which 

 Purkinje had discovered in the bird's egg. This conclusion led 

 him to draw a fundamental distinction between the elements of 

 reproduction in these two classes. It was not till 1834 that M. 

 Coste demonstrated in the ovule of Baer the existence of a distinct 

 germinative vesicle, and thus completed the discovery of the 

 German physiologist, or rather he assigned to it its true value, by 

 proving that the Mammalia, and Man himself, are propagated by 

 true ova or eggs, which may be compared, in all respects, to those of 

 birds. 



