(84) From the works of Baer, based on his opinions 

 about the system of animals and carried out in connection 

 with much later embryological investigations to the creation 

 theory of types, it is necessary to mention the major article 

 which is composed of seven independent reports: Beitrage zur 

 Kenntniss der niedern Thiere (Nova Acta phys. med. Acad. Caes. 

 Leopoldino Carolinae naturae curiosorum, T. 13, p. 2, 1827, 



S. 525-762). This work elucidated the description of dif- 

 ferent worms, parasitizing on molluscs, amphibiae and some 

 planarie and ended with the article "About congeneric rela- 

 tions of lower animals between themselves". 



In addition, Baer published some special zoological and 

 zootomical works, also connected in one way or another with 

 his subsequent embryological works. The following works are 

 from them: 



1. Ueber den Weg, den die Eier unserer Siisswassermuscheln 

 nehmen, urn in die Kiemen zu gelangen, nebst allgemeinen 

 Bemerkungen uber den Bau der Muscheln, Arch. Anat., Physiol., 

 1830, S. 313-352. 



Concerning the vexed question about the presence of orifice 

 in the ovary of the bivalve (or, by that time terminology, 

 headless) molluscs, Baer reported his observations, accord- 

 ing to which in many species of freshwater mussels these 

 openings are closed, although the way of transference of the 

 ova to the branchiate cavity in them is the same as in other 

 Lame 1 1 ibr anchiat a . 



2. Bemerkungen liber die Erzeugung der Perlen, Arch. Anat., 

 Physiol., 1830, pp. 352-357). In this paragraph, Baer 

 objected to Gom, who considered, that pearl-oysters are the 

 covers of the eggs of mussels. Baer found pearl-oysters only 

 in mantle and considered them as a manifestation of patholog- 

 ical process. (280) . 



(85) Both these editions represent at the present time 

 great rarity. In 1829, extracts of an inaccurate French 

 translation of both these works, performed by Breschet, 

 appeared ("Lettres sur la formation de l'oeuf dans l'esp&ce — 

 humaine et dans les mamiferes" "Commentaire de memoire 

 precedent", publies par Breschet, Paris). This edition was, 

 apparently, published in very few editions, that even Baer 



634 



