VARIETIES OF GENERATION. 



939 



the lapse of eleven years, and the same is true of anguilulae after twenty-eight 

 years. Spores and seeds can be placed in a state in which metabolic activity 

 is no longer demonstrable, and from which, as has long been known, they may 

 under suitable conditions, again germinate. According to Decandolle, vegetable 

 seeds may exhibit this property after from sixty to one ^hundred and fifty years. 

 Division takes place in many protozoa (amoebae, infusoria), and in such a 

 manner that, in accordance with the character of the cellular division, the organ- 

 ism, including its inner nuclear structure, and the cell-body, divides by an active 

 process into two organisms. Starfish (ophidiaster) divide spontaneously, or they 



FIG. 348. Cysticercus from Tasnia 

 solium with Everted Hollow Bud 

 (Cephalic Segment) : I a, caudal 

 vesicle (embryonal vesicle); b, the 

 head of the tapeworm with suckers 

 and ring of booklets (scolex); 

 cervical portion. .Enlarged 

 magnifying glass. 



FIG. 349. Portion of an Echino- 

 coccus-cyst with Brood-capsule: a, 

 capsule; b, parenchymatous layer; 

 c, brood-capsule filled with scolices 

 (Figs. 345-349 after Sommer). 



FIG. 350. Tsenia mediocanellata. 

 Natural size. 



eliminate an arm, which may develop into a complete animal. The artificial 

 division of lower forms of animal life and the development of the fragments into 

 entire beings were first demonstrated by Trembley in the hydra. 



Budding or sprouting takes place in most marked degree in polyps; but also 

 in infusoria (vorticellidas) and others. It consists in the sprouting of a bud- 

 like structure from the maternal body, which it gradually comes to resemble. 

 The bud-like formations either remain attached permanently to the maternal 

 organism, so that gradually a complete animal of considerable size is formed 

 (polypariae) , the bodies of the individual remaining directly connected with 



