158 NOTE ON ALTERNATION OF GENERATIONS 



of maintaining a separate existence, if this bond of 

 brotherhood be dissolved. But the grand peculiarity 

 is, that the solitary salpa produces chained salpse, 

 and the chained salpse produce the solitary salpa ; 

 nay, it has been ascertained, that invariably the 

 ovum of one of the chained salpse produces a so- 

 litary animal, while the ovum of a solitary salpa 

 produces the compound animal ; J or, as Charnisso 

 describes it, " A salpa-mother is not like its daughter, 

 or its own mother, but resembles its sister, its grand- 

 daughter, and its grandmother." 



The process of alternation exists among the En- 

 tozoa. It has recently been established that Intes- 

 tinal Worms, long regarded as specifically or generi- 

 cally distinct, are but one and the same animal. 

 Von Siebold was the first to announce, in' 1844, that 

 these creatures assume quite different forms, and 

 possess different habits, according to the kind of ani- 

 mal in which they live. " For example, the micro- 

 scopic egg or embryo of a Tcenia, evolved in the 

 intestinal canal of a dog or cat, if taken with food 

 into the stomach of a rat, finds its way invariably 

 to the liver, and becomes a Cysticercus ; while, if it 

 be swallowed by a sheep, it travels by some recondite 

 road to the brain, and is transformed into that para- 

 site so fatally known as producing the ' staggers,' 

 Ccenurus. Let either of these now, in turn, be swal- 

 lowed by the carnivorous quadruped, and a Tcenia, is 

 the invariable result." 2 



In 1856, Von Siebold published an account of 

 experiments with Moths and Bees, in which he main- 



1 Harvey's Sec.-Side Book, p. 234. - Gosse's Life, p 120. 



