THEORY OF THE GE&MPLASM 43 



SECOND GROUP OF FACTS. THE LOWER MULTI- 

 CELLULAR ORGANISMS. 



Although in the development of unicellular 

 organisms the way by which like begets like is plain 

 and intelligible enough, at least in the cases dealt 

 with, it is different with multicellular organisms, 

 which have reached a higher grade of development. 

 Among them we have to do with a continuous 

 process of development, in which the highly- 

 differentiated, multicellular organism arises from 

 an egg, and in turn gives rise to an egg, and so on in 

 unending sequence. But the succeeding stages of 

 the sequence are so exceedingly dissimilar in appear- 

 ance that the question how one step of the series 

 turns into the next, and, above all, the question how 

 the similarity of organisms, separated by the egg- 

 stage, can be transmitted through the egg-stage, 

 form the deepest riddle offered to biological investi- 

 gation. Here, in a completeness so wonderful that 

 our intelligence can hardly apprehend it, are pre- 

 sented to us the qualities of the organic material of 

 which cells are made. Here lies that dark secret 

 into which the various theories of generation try 

 to direct a beam of light, and seek to find out the 

 direction in which explanation may be found. 



An intermediate stage which may serve towards 

 the explanation of these circumstances is presented 

 by the lower multicellular organisms, such as 

 threadlike algse, fungi, and other simple creatures. 

 In them cells arise by division from the egg or 

 from the spore, and become united into an in- 



