290 GENERAL BIOLOGY 



been considering are mere accessories of birth and being. 

 Even the primitive vertebrates lack them all; they have 

 only eggs and sperms, and often merely scatter these free in 



the water, to develop 



Fig. 173. Diagram of the division -rTr-i-fVi/-.ii+ -fn-H-Vio-r t^o 

 of a paramoecium (after Jennings). ^itnOUt turthcr pa- 



a and 6 show loss of specific Charac- -ro-n-l-ol r^r\r, + r,r^+ r^r- i-r-> 



ters; c, d and e show division; /, g renxai COntaCt Or m- 

 and h show re-formation of one of ft^^(2,■nnf^ a n /\ tttV. oti 



the daughter cells. nucncc, ano wncn 



we reach the simplest 

 organisms, in some of them we find not even sex cells 

 but only protoplasm ; yet there appears to be faith- 

 ful reproduction of parental characters; and again 

 we are impressed with the fact that the primary 

 functions of life are functions of protoplasm. 



In chapter II we traced the origin of separate 

 germ cells. Let us now note certain fundamental 

 likenesses and differences of development with them 

 and without them. First, there is continuity of 

 living substance in either case. A part of the old 

 lives on in the new. The protoplasm out of which 

 new organisms are formxcd is potentially immortal. 

 Secondly, reproduction is, to a greater or less extent, 

 a new production in either case. Even the two 

 daughter cells of a protozoan are not merely halves 

 of a divided mother cell ; for the materials of that 

 cell have been reformed with more or less of change. 

 The unicellular organism undergoes regressive 

 change before division takes place; the specific 

 characters are lost, to be refashioned during the 

 adolescence of the new cell (fig. 173). The process 

 has been aptly likened by analogy to the dissolving 

 of a crystal in its mother liquor, to be subsequently 

 recrystallized out of it. 



On the other hand there are very considerable differences, 

 accompanying development by means of germ cells. These 



