570 POPULAR SCIENCE MONTHLY. 



observations upon the development of animals had progressed in 1672. 

 His are, doubtless, the earliest figures ever made showing the com- 

 paratively early stages of development. Harvey's observations on de- 

 velopment, published in 1631, were not accompanied by illustrations, 

 and the sketches of Fabricius, db aqua pendente, published in 1604, were- 

 far surpassed* by Malpighi's, the youngest stages represented being much 

 older than his. 



Fig. 3 shows a group of selected sketches from different plates,, 

 but they fail to give an adequate idea of the extent of the work, taken 

 as a whole. It is very interesting to note the figures showing the forma- 

 tion of the heart and aortic arches. The execution of the figures in this 

 work is less coarse than those on the silkworm. 



The embryological thought of his time was dominated by the theory 

 of preformation or pr.edelineation. Just as when we examine a seed, we 

 find within an embryo plantlet, so it was supposed that the minute 

 embryos of all animal life existed in miniature within the egg. Harvey 

 had expressed himself against it, and the doctrine was overthrown by 

 Wolff in the following century. Malpighi's position, however, was 

 based on actual observation; he was not able to find by examination any 

 stage in which there was no evidence of organization. Dareste says 

 that he examined eggs in a very hot August, in which there is reason 

 to believe that developmental changes had gone forward to a con- 

 siderable degree. Be this as it may, the imperfection of his instru- 

 ments and methods would have made it very difficult to have seen 

 anything definitely in stages below twenty-four hours. As a result of 

 his experience, he says: 



"When we undertake to discover the principle of life of animals in 

 the egg we are astonished to find the animal already formed there; thus 

 our labor is vain, for as soon as we encounter the first movement of life 

 we are obliged to recognize parts that are visible to our eyes. * * * 

 On this account, it may be necessary to declare that the first beginnings 

 preexist in the egg," etc. In his posthumous works he "is less circum- 

 spect, and goes even to the point of describing the mechanism of evolu- 

 tion of these primitive elements." 



Malpighi was a naturalist, but of a new type; he began to look 

 below the surface, and essayed a deeper level of analysis, in observing 

 and describing the internal and minute structure of animals and plants, 

 and when he took the further step of investigating their development 

 he was anticipating the work of the nineteenth century. 



JOIIX* SWAMMEKDAM. 1637-1680. 



Swammerdam was a different type of man — nervous, incisive, very 

 intense, stubborn and self-willed. Much of his character shows in the 



