GENERAL EMBRYOLOGY. 



141 



Division. In the case of division (cf. figs. 119, 122, 145) an 

 animal separates into two or more equivalent parts, so that it is 

 not possible to distinguish the mother and the daughter animal; 

 for the original animal has completely disappeared in the young 

 generation. The division is commonly a transverse one, in which 

 the plane of division stands perpendicular to the long axis of the 

 animal; less common is longitudinal division, rarest is oblique 

 division (the planes of division passing in the direction of the long 

 axis, or forming an acute angle with it). 



Budding. In the case of budding, the products are unequal. 

 One animal maintains the identity of the mother animal; on the 

 contrary, the bud, the outgrowth caused by local increase, appears 

 as a new formation, as the daughter individual. Yet the differ- 

 ence between division and budding is bridged by intermediate 

 conditions; for, if we start with binary division, this will approach 

 budding in the same degree as the division products become 

 unlike, so that the one takes on more and more the character of a 



FIG. 90. A, Hydra grisea in optical section with a bud ; also B, first stage of a bud. 

 i, entoderm; ek, ectoderm; s, supporting lamella; t', tent 



VIV) 0UWUV*4U) C/rif, Cl^ UV^VACI. iAA , O, QU.pJJUL Llllft ICUUOUO. ^ 



mal; ", tentacle of the bud; TU, stomach; o, mouth. 



tentacle of the mother ani- 



bud, the other retaining the character of the mother organism. 

 Such transitions are chiefly possible in the case of terminal 

 budding, where the buds appear at one. end of the main axis of the 

 maternal organism. The character of budding is, on the contrary, 

 unmistakable if the buds arise as lateral outgrowths of the mother 



