of posterity of starfish (Asterias sanguinolenta and 

 A, angulosd) , mentioned that he turned for advice to Krohn 

 because he wished to confirm the authenticity of his dis- 

 covery (M. Sars. Uber die Entwickelung der Seesterne, 

 Arch. Anat., Physiol., 1842, S. 328) (563). 



(134) In the monograph "Embryological investigations 

 on medusa" I. I. Mechnikov wrote, that the situation about 

 the development of the hydroidal polyps without alternation 

 of generations "could be also distributed on akalef after 

 that, Krohn obtained young medusae of Pelagia directly from 

 the eggs. This observation proved to be mainly astonishing, 

 because Pelagia nootiluoa was very similar to Chrysoara; 

 alternation of its generations was established by works of 

 Daliel and Bush" (p. 283) . In another place, Mechnikov 

 wrote: "On Pelagia nootiluoa, it was proved for the first 

 time that there were medusae which developed directly from 

 eggs. Later on, this discovery was confirmed by Agassits 

 (on P. oyanella) , Kovalevsky (on P. nootiluoa) and Meckel 

 (on P. perla)" (p. 388) (570). 



(135) One year before this, in the work, dedicated to 

 the larvae of molluscs, Krohn also mentioned pilidium which 

 he considered "larva of Nemertes in the broader sense of 

 the word" (p. 468), and actinotroch as larva of this worm 

 living in the duct of Polychaeta (572) . 



(136) In the work of Darwin "Observations on the 

 structure and propagation of the genus Sagitta" (Ann. nat. 

 hist., 13, 1844, p. 1-6) . 



The Russian translation of this article, see: Charles 

 Darwin. Works, V. 2, idz. AN. SSSR, 1936, pp. 95-102). 

 As Krohn noticed fairly—for the eggs of Sagitta, Darwin has 

 truly assumed the pelagic span of this fish (573) . 



(137) Krohn stated the list of the seven species of 

 Salpa, from which it is clear, that forms, described by 

 different authors under different specific names, in many 

 cases are, indeed, sexual and asexual generations of the 

 same species. 



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