CONDITIONS OF GAMETE FORMATION 



385 



the laboratory under uniform conditions, provided with abundant 

 food and prevented from undergoing fission, the animals often con- 

 tinue to grow until they are fully twice as large as the largest found 

 under natural conditions, and a considerable number of these very 

 large animals develop the hermaphroditic sexual organs character- 

 istic of the species, become sexually mature, and lay eggs. Often 



FIG. 196. Manubrium of female Lizzia (jelly-fish), showing agamic buds and 

 eggs: in addition to the four large eggs, o, those regions which are occupied by dis- 

 tinctly differentiated ovarial cells are indicated by drawing in cell outlines and nuclei; 

 in the dotted regions are cells which may become either buds or ovarian cells: roman 

 numerals I, 111$ IV, V, VII, indicate buds in the order of their formation, bud I having 

 already become free and buds II and VI being on the other side of the manubrium; 

 the point * indicates the position where the eighth bud should appear. From Braem, 

 'oS. 



sexually mature animals can be made to undergo fission simply by 

 transferring them to another perfectly clean aquarium without 

 slime on its walls, and when the level of fission is anywhere near the 

 openings of the sexual ducts, which lie a short distance behind the 

 mouth, the openings and all the terminal organs disappear. 



The very low susceptibility of the sexually mature animals to 

 cyanides, as compared with that of the largest animals in nature, 



