368 Prof. Valentin's Beport on the Progress of Embryology, 



Description of Plate VI. 



Fig. 1. Superior anteniise of Munna Kroyeri. 



2. Munna Kroj'cri. 



3. Nat. size of do. 



4. Inferior antennsc of Munna Kroyeri. 

 6. First or prehensile pair of legs. 



6. Abdominal branclius, a, appendage. 

 ... 7, 8, 11, 12, 10, Parts of the mouth. 



9. Abdominal plate. 

 ... 10. Ambulatory leg. 

 ... 14. Abdominal segments. 

 ... 16. Evadnc Nordmannii, a, nat. size. 

 ... 16. Anterior part of body of an Evadne. 

 ... 17. Pasithoj Vesiculosa, a, nat. size. 

 ... 18. Rostrum, palp, and oviferous legs of do. 



Extracts from Professor Valentines Beport 07i the Progress of 

 Embryology in the year 1840.* 



Some interesting discoveries rendered the past year a high- 

 ly productive one for embryology. Two main problems which 

 engaged the various physiologists here occupy the foreground ; 

 namely, the earliest development of the Manunalia, and the 

 metamorphoses of the germinal membrane in its transforma- 

 tion into the embryo. ***** So long as the meta- 

 morphoses of the germinal vesicle following fecundation could 

 be considered only hypothetically, it was assumed that the 

 Purkinjean [germinal] vesicle either burst and poured out its 

 contents, or became flattened ; and now in one of these two 

 Avays contributed to the formation of the germinal membrane. 

 Both theories had been put forth before the discovery of the 

 germinal spot. But when the existence of the latter became 

 known, the discoverer said, that probably the macula germi- 

 nativa represented the first foundation of the germinal mem- 

 brane. This conjecture obtained more probability from the 

 obvious fact, that the number, size, and distribution of the 

 germinal spots alternated according to the different stages. 

 Research, however, first in the mammaha, and then in rep- 

 tiles and fishes, shewed that, in consequence of fecundation, 



* Repertvriuiu f r Anaiomie unci Physwlcgic. Jabrgang, 1841. 



