56 THE EVOLUTION OF MAN. 



fcained to the present time only by the Amphioxus, while 

 all other Vertebrates have assumed a modified kenogenetic 

 form of cleavage. (Cf. Table III., voL i. p. 241.) The latter 

 certainly originated at a later period than the former, and 

 the egg-cleavage of the Amphioxus is, therefore, extremely 

 interesting (vol. i. p. 442). In this the parent-ceU first 

 parts into two similar ceUs, the two first cleavage-cells 

 (Fig. 169, A). From these, by continuous division, arise 

 4, 8, 16, 32, 64 ceUs, etc., etc. (Fig. 169). The final result of 

 this primordial cleavage was, we found, the formation of a 

 globular mass of cells, which was entirely composed of homo- 

 geneous, undifierentiated cells of the simplest characfter 

 (Figs. 170, and 171, E), On account of the resemblance 

 which this globular mass of cells bears to a mulberry or 

 blackberry, we called it the " mulberry-germ," or morula. 



This "morula" evidently at the present day shows us 

 the many-ceUed animal body in the same entirely simple 

 primitive condition in which, in the earlier Laurentian 

 primitive epoch, it first originated from the one-ceUed 

 amoeboid primitive animal form. The morula reproduces, 

 in accordance with the fundamental law of Biogeny, the 

 ancestral form of the Synamoeba. For the first cell-com- 

 munities, which then formed, and which laid the first 

 foundation of the higher many-ceUed animal body, must 

 have consisted entirely of homogeneous and quite simple 

 amoeboid ceUs. The earliest Amoebae lived isolated hermit 

 lives, and the amoeboid cells, which originated &om the 

 division of these one-celled organisms, must also have long 

 lived isolated and self-dependent lives. Gradually, however, 

 by the side of these one-celled Primitive Animals, small 

 amoeboid conununities arose, owing to the fact that the 



