ZOOLUGV AND liOTANY, JMIGKOSGOPY, KTU. 601 



the exact region to be occupied bj this plexus. The interceHular spaces 

 thus formed enlarge and fuse together to form lymphatic lacunae. At a 

 later stage the lacunte acquire an endothelial lining, and become the 

 isolated primordia of the lymphatic plexus. 



Development of the Kidney in Chelonia. * — T. H. Burlend has 



studied this in Ckelone viridis and Ckrysemys marginata. The prone- 

 phric tubules arise from the somatic layer of the nephrotome, from a 

 primitively continuous primordium. The origin of the mesonephric 

 tubules is twofold : the portion nearest the segmental duct arises from 

 the somatic layer of the nephrotome, and the other portion from the 

 coelomic end of the nephrotome. The glomus is formed between the 

 aorta and pronephric tubule openings, the glomeruli have a covering 

 originating from the splanchnic wall of the nephrotome. 



Development of Lungs in Pelobates fuscus.t — M. Makuschok 

 finds that the original position of the lung-primordia in this Amphibian 

 is bilaterally symmetrical. The appearance of definite diverticula is 

 late — at the time when five pairs of branchial pouches are established. 

 The early development of the lung-primordia is quite analogous to the 

 fourth and fifth pairs of branchial pouches. After the appearance of 

 the lung-primordia, and before those of the fifth pair of branchial 

 pouches, there is evidence of an unimportant pair of diverticula — -the 

 rudiments of the sixth branchial pouches. 



Development of Pelvic Fins in Exoccetus.^ — K. Derjugin and 

 E. Rozhdestveusky find evidence in the development of this fiying-fisii 

 that the cartilaginous elements which lie topographically in the position 

 of a pelvic girdle, but are usually regarded as coalesced basalia, are 

 genuine representatives of a pelvic girdle, homodynamous with the 

 scapula and coracoid of the pectoral girdle. 



Hatching of Goldfish Egg.§- P. Wintrebert has observed in the 

 <jase of the goldfish {Carassius auratus) what he observed in the trout, 

 that the unicellular glands of the embryo's skin secrete before hatching 

 a peri-embryonic fluid which has a digestive action on the shell- 

 membrane. It becomes more delicate and readily broken without any 

 voluntary movement on the part of the larva. 



Development of Thymus in Selachians. |1 — A. Maximow has 

 studied this in ScylUum and Raja. The primordia arise as endodermic 

 placodes on the dorsal margins of the gill-clefts. The small thymus- 

 cells have, as Hammar maintained, a genuine lymphocyte nature and a 

 mesenchymatic origin. He shows that the thymus is to begin with a 

 purely epithelial organ. It is invaded by migratory mesenchyme cells 

 • — the lymphocytes — and it offers them conditions for their prolific 

 multiplication. In Selachians, as in other cases, the thymus furnishes 

 lymphocytes to the blood. 



* Anat. Anzeig., xli. (1912) pp. 497-510 (15 figs.), 

 t Anat. Anzeig., xlii. (1912) pp. 59-70 (6 figs.). 

 X Anat. Anzeig., xli. (1912) pp. 643-7 (2 figs.). 

 § C.R. Soc. Biol. Paris, Ixxii. (1912) pp. 70-3. 

 \ Arch. Mikr. Anat., Ixxx. (1912) pp. 39-88 (5 pis.). 



