130 1)». E. KLEIM. 



a considerable measure genetically derivatives from the para- 

 blast. This last fact is also insisted upon by Balfour, who, 

 however, incorrectly, as we have proved, considers the para- 

 blast as a part of the yolk. 



Now, the deeper layers of the peripheral thickening of the 

 archiblast are, as is well known, in the embryo — which is 

 developed out of a portion of that peripheral thickening — 

 used for the formation of the hypoblast ; from this and from 

 what I have shown with reference to the parablast, the asser- 

 tions of Lereboullet (feuillet muqueux), Kupfer, and Van 

 Bambeke, with reference to the alimentary canal, receive 

 their due significance. 



From the presence of parablast, after a certain stage, beneath 

 the whole extent of the archiblast — embryo and yolk-sac — it is 

 only natural to draw the inference that within the area of the 

 latter, i. e. the yolk-sac, notorious for the development of 

 blood and blood-vessels, the parablast is concerned in the 

 formation of blood and blood-vessels. But whether the 

 elements derived from the parablast and contained in the 

 deeper layers of the embryo are destined to be ajso material 

 for the formation of connective and kindred tissues, is a 

 conjecture which requires further consideration.* 



Bibliography . 



1. Carl Fogt. — "Embryologie des Salmones," in "Histoire Naturelle des 



Poissons de i'Europe Centrale.' Par L. Agassiz. 1842. 



2. M. Lereboullet. — " Recherches d'EmbryoIogie coraparee sur le Developpe- 



ment de la Truite, du Lezard et du Limnec," in ' Anuales des Sciences 

 Naturelles,' quatrieme serie, Zoologie. Tome xvi. 



3. S. Strieker. — " Untersucbungen iiber die Entwicklung der Bacbforelle," 



' Sitzungsberichte der Wiener Kais. Academic d. Wissenschaften.' 1865. 

 Bd. 5l/ii. 



4. C. Kupfer. — " Beobacbtungen iiber die Entwicklung der Knochenfiscbe," 



'Max Scbultze's Archiv.' Bd. iv. 



5. Bieneck. — " Ueber die Schicbtung des Forellenkeims," 'Max Scbultze's 



Arcbiv.' Bd. v. 



6. Goette. — " Zur Entwickelungsgescbicbte der Wirbeltbiere," ' Vorlaufi^e 



Mittbeilung in Ceutralblatt f. Medicin. Wissenscbaften.' 1869. No. 26. 



7. E. Klein. — " Researcbes on tbe First Stages of tbe Development of ibe 



Common Trout (Salmo fario)," read before tbe Royal Microscopical 

 Society, Marcb 6, 1872. 'Monthly Microscopical Journal.' 



8. Van Bambeke. — "Premiers effets de la Eecondation sur les ceufs de 



Poissons : sur I'origine et la significatione du feuillet muqueux. ou 

 glandulaire cbez les Poissons Osseux ; Seance de I'Acaderaie des 

 Sciences, 15 Avril, 1872," ' Comptes Rendus des Seances de 1' Aca- 

 demic des Sciences.' Tome Ixxiv. 



9. C. Weil. — " Beitrage zur Kenntnis der Entwicklung der Knocbenfiscbe," 



* p.S. — After this paper was in print I received the full monograph of 

 Van Bambeke's research on Teleostean fishes. His observations on the 

 earlier stages of development have not been noticed in this paper, since they 

 are not contained in his earlier communication. 



