Cyclical Propagation. xv 



organisms was first discovered by Chamisso^ the author 

 of Peter Schlemihl/ whoin 1815 accompanied the Chan- 

 cellor Rumjanzow's expedition as naturalist in a voyage 

 round the world. He noticed that among the Salpae 

 a solitary salpa gave rise to a generation of a different 

 form, united in chains of twenty or more, and that each 

 link of this ^associated' form again produced the 

 'solitary' form. He concluded that all solitary salpae 

 produced chains, and on the other hand that all those in 

 associated chains were the parents of solitary ones ; so 

 that a salpa mother was not like its daughter or its own 

 mother, but resembled its granddaughter and its grand- 

 mother. At first the accuracy of Chamisso's observations 

 was doubted, chiefly for the reason that no similar 

 phenomenon was then known in nature. By degrees, 

 however, facts began to accumulate ; in hydroids and 

 flukes similar generation-cycles were obser\^ed, and in 

 1842 Steenstrup" collected all that was known on the 

 subject of alternating generations into a monograph 

 published in Danish and subsequently translated into 

 German and English. He described this mode of 

 reproduction as ' a peculiar form of fostering the young 

 in the lower classes of animals.' 



In 1849 the late Professor Owen ^ suggested the 

 existence of a residual germ-force in the cells of the 

 apparently asexual generation, and thought that alter- 

 nating generations were due * to the retention of certain 

 of the progeny of the primary impregnated germ-cell, or 

 in other words to the germ-mass, with so much of the 

 spermatic force inherited by the retained germ-cells from 



^ Adalbert de Chamisso, De Am'mah'bus, Fasc. i, De Salpa, Berlin. 

 1819. 



- J. J. S. Steenstrup, Ucbcr den Generationswechsel, Kopenhagen, 

 1842, and Ray Society, 1845. 



^ R. Owen, Parthenogenesis, 1849. 



