478 Miscellaneous. 



form of a tube. This tube persists until the later stages of deve- 

 lopment, and grows in length with the whole cervical region 

 without increasing in circumference, so that it finally constitutes a 

 long, thin, caudally directed, cervical, fistulous canal. In young 

 developmental stages of snakes and lizards we certainly meet with 

 a similar canal in a rudimentary condition ; in these forms, how- 

 ever, it undergoes no further development, but disappears much 

 earlier. 



7. The third branchial pouch swells out into an epithelial follicle, 

 with many secondary evaginations. This becomes constricted off 

 from the branchial gut, and the evaginations transform themselves 

 into thymus-tissue, in the interior of which, however, the central 

 epithelial follicle persists. The latter may be regarded as the 

 homologue of the carotid body in the lizards. 



8. The fourth and fifth branchial pouches develop jointly with 

 the above-mentioned supra-pericardial evaginations from a lateral 

 caecum-shaped fold at the posterior end of the branchial gut 

 {recessus prn^cerviccdis), similarly to what is found to be the case in 

 snakes. They soon become entirely constricted off from the 

 branchial gut, and in this manner form a complex of three epithelial 

 vesicles in connexion one with the other. Now, if their further 

 development also takes place on the same lines as in the siiakes, the 

 two foremost of these vesicles, which represent the remnants of the 

 fourth and fifth branchial pouches, should develop into thymus-tissue, 

 while the third and hindermost should, on the contrary, remain in an 

 epithelial condition. This, however, is not the case : all three 

 retain an epithelial character, and are met with in this shape, even 

 in much later developmental stages, between the aortic and pulmo- 

 nary arches. They do not come into connexion with the thyroid. 



9. The aorta develops from the artery of the fourth branchial 

 arch, the pulmonary artery from that of the sixth. The fifth aortic 

 arch, the rudiment of which arises between the fourth and fifth 

 branchial pouches, very soon becomes aborted again, as I have also 

 shown to be the case in snakes and lizards. 



10. The observations here detailed confirm the theories as to the 

 probable origin of the thymus and of the epithelial rudiments in 

 the cervical region, which I arrived at in the anatomical investiga- 

 tion of young turtles, and to which I have already drawn attention 

 in a previous memoir (" Beitrage zur Kenntnis der Halsgegend bei 

 Reptilien : I. Anatomischer Teil," published in ' Eijdragen tot de 

 Dierkunde, uitgegeven door het Genootschap Natura Artis Magistra 

 te Amsterdam,' 1880). — Anatomischer Anzeiger, viii. Jahrg., nos. 23 

 and 24, October 10, 1893, pp. 801-803. 



Observations on the Karyolcinetic Phenomena in the Cells of the 

 Blastoderm of Teleosteans. By MM. E. Bataillon and E,. Kcehler. 



In a previous communication we have described the results of our 

 researches upon the extension of the blastoderm on the surface of 



