ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 489 



ink-sac of the Cephalopoda, and this view is strengthened by a 

 consideration of the nervous supply. In the Gastropoda the glands in 

 question receive filaments from the " asymmetrical centre," in the 

 Cephalopoda the nerves come from the visceral or inferior ganglion 

 which corresponds exactly with that centre. 



If we compare the ink-sac of the Octopoda with that of the Deca- 

 poda we find that there is in the former an arrest of development, 

 the reservoir not being elongated or widened out ; in consequence of 

 this close relations still obtain between it and the anal orifice, and the 

 gland and reservoir are closely applied to one another. It is to be 

 borne in mind that the tetrabranchiate Cephalopoda are without the 

 organ, and that it is only some of the Gastropoda which possess one, 

 and that that one is always much simpler in character. 



The physiology of the question is also dealt with, and it is pointed 

 out that three stages may be distinguished in the excretion of the 

 ink: (1) there is a continuous passage of ink from the gland into 

 the vesicle — due to a vis a tergo, and to the compression exercised 

 by the limiting membrane of the gland and the nodosity of the 

 vesicle ; (2) an intermittent passage of the ink from the vesicle into 

 the sac, due to the contraction of the vesicle ; (8) spasmodic expul- 

 sion of the ink by the funnel, due to the spasm of expiration. The 

 nerve-branches from the visceral nerves were found to be motor 

 filaments, presiding over the contraction of the wall of the vesicle. 



Sense of Colour in Cephalopoda.* — How highly developed the 

 sense of colour is in insects has been shown by Sir John Lubbock 

 in his interesting observations on bees, wasps, and ants. For the 

 development of the same sense in animals of a different type C. Keller 

 brings forward evidence taken from the cuttle-fishes, which manifest 

 in a high degree the power of adapting the colour of their skin to 

 that of the environment. Keller was able to observe this adaptation 

 of colour in Eledone. In the Naples Aquarium a specimen of this 

 Octopod was under the necessity of flying from a powerful lobster ; 

 during its flight it appeared pale red ; but subsequently, resting on a tuft 

 of yellow rock covered with brown spots, it imitated the yellow ground- 

 colour with its brown spots so closely that it became almost invisible 

 to the observer. In this case the conditions were decidedly very 

 favourable for the occurrence, for yellow and dark-brown colour-cells 

 occur in Eledone in large numbers. It should be added that the 

 eye of the cuttle-fish shows an unusually high development. 



'Foot' of certain Terrestrial Gastropoda. f — Mr. J. Wood- 

 Mason describes the structure of the part of the foot called by 

 German writers on malacology the Fuss-saum which, as no technical 

 name for it appears to exist in the English language, he proposes to 

 call the peripodium, in allusion to its relation of position to the 

 locomotor ventral surface or foot of the molluscs possessing it, but 

 which he thinks may be homologous with the lateral folds (epipodia) 



* Vierteljahresschr. Naturf. Gesell. Zurich, xxvi. (1881) p. 100. Cf. Xatur- 

 forscher, xv. (1882) p. 40, 



t Proc. Asiatic Boc. Bengal, 18S2, pp. GO-2. 



