384 Proceedings of the Royal Physical Society. 



necessary along the dorsal suture before the soft parts can 

 he withdrawn, whereas in younger specimens, with a thinner 

 cephalothorax, the absorption of a portion of the cement of 

 the dorsal suture may be sufficient to allow of the requisite 

 amount of play. Should this be the case, we have a solution 

 of the difficulty, that whereas the cephalothorax splits along 

 the dorsal suture in some cases, it certainly does not do so in 

 others. It appears to me that the same argument applies to 

 the membranous parts of the chelate limbs. Whether or 

 not these rupture during ecdysis, I regard as depending 

 mainly on age. In young specimens the membranes are 

 comparatively thin, and capable of a considerable amount of 

 tension without injury, whereas in older and thicker mem- 

 branes rupture may take place owing to want of elasticity. 



List of Eeferences to Literatuee. 



1. Sur les diverses reproductions qui se font dans les Ecrevisses, les Omars, 



les Crabes, &c. M. Reaumur, Mem. de VAcad. des Sciences, 1712, 

 Paris, 1814. 



2. Observations s. 1. mue des Ecrevisses. M. Reaumur, I,Um. de VAcad, 



des Sciences, 1718. 



_ 3. On tlie Process of Exuviation and Growth in Crabs and Lobsters. 

 J. Couch, Cornwall Pohjtechn. Soc. Trans., 1843. 



4. Short Account of the Mode of Reproduction of Eost Parts in the 



Crustacea. H. D. S. Goodsir (Wernerian Soc, Dec. 1843), Ann. Nat. 

 Hist., Ser. i., voL xiii., 1844. Vide also Brit. Assoc. Reiwrt, 1844. 



5. Nouvelles observations sur les Ecrevisses (part refers to reproduction of 



lost parts). M. Chantran, Comptes rendus, Ixxiii., 1873. 



^ 6. U. d. histol. Vorgange bei d. Hautung von Asiacns fluviatilis. Max. 

 Braun, Wilrzhurg Arleiien, Bd. ii. 



7. The Crayfish. T. H. Huxley. London, 1880, 



8. Rech, s. 1. structure et 1. formation des teguments chez les Crustaces 



decapodes. A. N. Vitzou, Arch, de Zool. Exper. et Gen&r., tome x., 

 1882. 



_^ 9. Report of Committee appointed to explore the Marine Fauna and Flora 

 of South Coast of Devon and Cornwall No, 2, C. Spence Bate, 

 Reporter— ^r^Y, Assoc. Report, 1867. 



10. Report on the Present State of our Knowledge of the Crustacea, Pl, iii, 

 C. Spence Bate, Brit. Assoc. Report, 1877. 



