ZOOLOGY AND BOTANY, MICROSCOPY', ETC. 461 



Swim-bladder of Teleosts.* — II. C. Tracy finds that the Clupeoid 

 swim-bladder is like that of the carp : it consists of a posterior portion 

 which represents the primitive swim-bladder, and an anterior secondary 

 outgrowth. That of Fundidas and Menidia is like that in Esox, but 

 without pneumatic duct. 



The epithelial lining is derived from the endoderm of the oesophagus ; 

 the splanchnic mesoderm contributes the inner and middle layers of the 

 Avail ; the outer connective tissue layers originate from the somatic; 

 mesenchyme of the neighbouring body region ; the longitudinal bands 

 of striated muscle in the swim-bladder of Opsanus arise from the myo- 

 tome of the first somite and are innervated by a branch of the first 

 spinal nerve. 



In the more primitive swim-bladders the pneumatic duct opens into 

 the anterior end ; in the derived types the embryonic pneumatic duct 

 opens into the posterior end. The posterior chamber in Opsanus, Sipho- 

 stoma, Tautoglabrus and Tautoga develops directly from the embryonic 

 pneumatic duct. 



The pneumatic duct in the eel, the posterior chamber in Opsanus, 

 etc., and the oval in the highest type of swim-bladder are probably to 

 be regarded as homologous structures, produced as the result of the 

 progressive reduction of the pneumatic duct and the development of a 

 rete mirabile. 



In the primitive swim-bladders the epithelial lining is undifferen- 

 tiated ; in the eel, the epithelium has become columnar and is thrown 

 up into simple folds all over the internal surface. The red gland in the 

 higher types results from a progressive increase in the complexity of the 

 folding, accompanied by a concentration of the folds in a restricted area. 



Tunicata. 



Tenacity of Life in Ciona intestinalis.f — G. Daumezon has found 

 it possible to keep this hardy Ascidian in good condition in artificial 

 sea-water. His experiments led him to discover evidence of extraordi- 

 nary tenacity of life. They are vigorous for hours at 20-2:5° C, and 

 they survived cold till the medium froze. In a solution of saccharose 

 of the optimum density the animals showed the heart beating for several 

 hours. They can live out of water for hours, till they lose the water 

 they contain. 



INVERTEBRATA. 



Mollusca. 



Marine Molluscs of Clare Island.! — Nathaniel Colgan deals with 

 21G species from this area, which has recently been the subject of a 

 detailed regional survey. He discusses the somewhat negative charac- 

 teristics of the Clare Island marine molluscan fauna and compares it 

 with that of Dublin Bay. The western area has 5 boreal species to 

 31 austral ; the eastern or Dublin area has 12 boreals to 37 australs. 



* Anat. Anzeig., xxxviii. (1911) pp. G38-49 (10 figs.). 



t C.R. Soc. Biol., lxx. (1911) pp. 721-3. 



% Proc. R. Irish Acad., xxvi. (1911) Clare Island Survey, pt. 22, pp. 1-36. 



Aug. 16th, 1911 2 h 



