284 PHYSIOLOGY OF THE INVERTEBRATA. 



The author has confirmed MacMunn's investigations, and 

 he has also proved the renal function of the nephridia in 

 Limax mciximus, Heli/:^ pomatia, Limax varicfjatns, Arion 

 atei\ and other Gasteropods. They contain, in addition to 

 uric acid, urea and calcium phosphate. Many of these 

 organs also contain some of the histoh^matins ; and in the 

 case of " Avion ater the nephridium showed a spectrum 

 resembling that of myohgematin, and this spectrum is 

 remarkable for its resemblance to that of the kidney of 

 Vertebrates." (MacMuun.) 



The Gasteropoda are provided with numerous glands which 

 secrete mucus. The epiphragm of Helix is secreted by 

 mucous glands, but it becomes hardened and strengthened 

 by the deposition of calcareous matters. This epiphragm 

 (perforated) is secreted before hybernation (ix., the winter 

 sleep), and closes the shell-opening when the animal is 

 retracted. The epiphragm is cast off in the spring when the 

 animal awakes. 



The secretion of the mucous glands of slugs is of value to 

 the animals as a means of protection against the attacks of 

 enemies. The mucus secreted is often pigmented, and it 

 gives a polished appearance to the pigments which resemble 

 certain metallic hues ; such joigments are spoken of as protec- 

 tive colours. 



Having referred to certain secretions of the Pidmogastcro- 

 'poda, we have now to consider those of th.eBranchiogastcropoda. 



The author* has investigated the nephridia of Patella 

 vuhjata. These organs consist of two parts — left and right 

 lobes. The left nephridium is very small in comparison to 

 the right. The anatomy and histology of these organs have 

 been fully described by Professor E. Kay Lankester, F.R.S.,t 

 J. T. Cunningham,! and Harvey Gibson. § 



* Procee(li»f/s of lioyal Society, vol. 42, p. 392. 



t Annals and Magazine of Natural History, vols. 20 (1S67), and 7 (18S1). 



t Quarterly Journal of Microscopical Science, vol. 22, p. 369. 



§ Transactions of lioyal Society of Edinhuryh, vol. 32, p. 617. 



