154 Miscellaneous. 



indicate that secondary digestive phenomena may take place in it. 

 The reaction of the contents is neutral or alkaline. 



The second, wider portion of the terminal intestine only performs 

 the function of a stercoral reservoir. It is associated, for example in 

 the Dytiscidse, the Nepce, and the Ranatrce, with a voluminous caecum, 

 which is not a natatory bladder as has been supposed. It may be 

 empty or full of liquid, but never contains any gas. The liquid pro- 

 duct secreted by the Malpighian tubes accumulates there, and, under 

 certain circumstances, deposits in it calculi which may be of consider- 

 able size. 



Some substances resist the digestive action and are passed with the 

 excrements. Such are the chitine of the integuments of insects, vege- 

 table cellulose, and chlorophyl ; the microspectroscope enables us to 

 detect the last at all parts of the alimentary tube of herbivorous 

 insects. 



Insects have nothing resembling the chyliferous ducts. The pro- 

 ducts of digestion, dissolved salts, peptones, sugar in solution, and 

 fatty emulsions, traverse the comparatively thin coats of the diges- 

 tive tube by a phenomenon of osmosis, and mix with the blood outside 

 this tube. 



The Malpighian tubes are exclusively depuratory and urinary 

 organs, which free the body from the products of the wear of organic 

 elements. The liquid that they secrete contains urea (doubtful), 

 uric acid, urates in abundance, hippuric acid (doubtful), chloride of 

 sodium, phosphates, carbonate of lime, oxalate of lime in quantity, 

 leucine, and colouring-matters. 



As to the so-called anal glands, the product they secrete is very 

 variable in different groups ; but it has no part to play in digestion, 

 and is not urinary. 



On the Structure and the Development of the Sting and Ovipositor 

 of some Hymenoptera and of Locusta viridissima. By Dr. H. 

 Dewitz. 



It has generally been admitted, until within the last few years, 

 that the parts which are found at the posterior extremity of the 

 bodies of insects, and which constitute nippers, cerci, the ovipositor, 

 and the sting, are formed by the transformation of certain segments, 

 or at least of some arches of segments. However, new views as to the 

 origin and signification of these organs were introduced into science 

 in 1866 by Packard and Weissmann. Memoirs directly or indirectly 

 relating to this subject have been published more recently byGanin 

 in 1869, and lastly by Oulianiu and Krapelin in 1872 and 1873. 



The embrylogical researches of M. Dewitz, which relate to 

 Locusta viridissima, Apis mellifica, Bombus sp., Vespa vulgaris, 

 and Cryptus migrator, have led him to the discovery of some impor- 

 tant facts, which confirm, in a general way, the opinion of the ana- 

 tomists whom we have just mentioned, completing and rectifying 

 certain points of their observations. To give an idea of the results 



