AND THE LOWER ANIMALS. 197 



of the list of modern naturalists when we refer to 

 marine animals — described the development of two 

 Asterias (Asterias sanguinolenta and Aster acanthion 

 Millleri) . He saw these Echinoderms, contrary to the 

 rule among animals so low in the scale, absolutely, 

 in some measure, hatch their own ova. He proved 

 that the larva springing from the latter, at first 

 resembled an infusorian, and afterwards presented 

 the appearance of an animal composed of two lateral 

 symmetrical halves, which at a later period became 

 converted into a radiated creature.* Shortly after, 

 the celebrated embryologist Baer tried the effect 

 of artificial fecundation on the sea-urchins, but was 

 only able to observe the earlier stages of develop- 

 in ent.f Almost at the same period two inhabitants of 

 Marseilles, Messrs. Dufossef and Derbes,§ observed 

 nearly similar phenomena in the sea-urchins ; but the 

 figures of the second are very different from those 

 of Saars. Two Norwegian naturalists, Koren and 

 Danielssen, discovered at this period that the Bijpin- 

 naria asterigera was a developmental phase of the 

 true Asterias. \\ Finally, in 1845, J. Mliller, the cele- 

 brated Berlin plrysiologist, investigated the marine 

 animals of the North Sea at Heligoland; described 



* " Memoire sur le Developpement des Asteries," translated in 

 the " Annales des Sciences naturelles," 1844. 



t " L'Institut," 1845. 



X " Observations sur le Developpement des Oursins," in the 

 " Annales des Sciences naturelles," 1847. 



§ " Observations sur les Phenomenes qui accompagnent la For- 

 mation de rEmbryon chez l'Oursin comestible," 1848. — Annales 

 des Sciences naturelles. 



|| "Observations sur la Bipinnaria asterigera," printed in Swe- 

 dish in 1847, and translated into French in the same year. 



