NOTES AND MEMORANDA. 401 



longitudinal layer connected with the columella, and of function in 

 withdrawing the animal into its shell. 



The retractile bundles are chiefly innervated by the pedal 

 ganglia, which are, moreover, the chief centre for the locomotor 

 muscles also ; these pass in two parallel rows into the foot, and are 

 given off to the muscles by pairs, and at regular distances from one 

 another. When a motor nerve is stimulated the muscle-serum be- 

 comes less capable of dissolving myosin, and the consequent coagula- 

 tion, which is always associated with extension of the protrusile 

 muscle, causes a change in the characters of the light reflected from 

 the foot ; with each stimulation this coagulated spot varies in position 

 according as different nerve-branches are excited, and this coagulation 

 extends from behind forwards. For further details the paper, which 

 is a very valuable contribution to this branch of j)hysiology, must be 

 consulted ; but we may point out that Herr Simroth observes that the 

 difiference noted between the living protrusile and retractile fibres is 

 evident also in the dead animal, the former being elongated, and the 

 latter greatly contracted. 



Auditory Organs of the Heteropoda. — Professor Claus opposes* the 

 views of Professor Ranke on three points : (1) According to this latter 

 observer there are only four auditory cells, in addition to the large 

 central cell ; Claus thinks that there are a large number. (2) The 

 structures regarded by Eanke as ganglionic are the concentrically 

 arranged auditory cells in the thickened sensory epithelium, into 

 which the fibres of the auditory nerve pass. (3) There is not a 

 single plate in the relatively large cavity between the central cell 

 and the outer auditory cells, but four large indifferent supporting 

 cells. It is of course impossible to make the diflerences plain with- 

 out reproducing the figures, and we must be content with drawing 

 att-^ntion to the subject. 



Peculiarity in Littorina. — In a paper " On some Australian 

 Littorinidfe " | the Rev. J. E. Tennison- Woods says that there is one 

 peculiarity in some members of this genus to which attention has not 

 been drawn by any naturalist, and it is so very common and so peculiar 

 that it must have some relation to the animal economy. It consists 

 of a spiral white or yellow line or groove, which lines the interior of 

 the shell and arises from the anterior aperture, or at the lower part 

 of the labrum or outer lip. Along the groove the organs of reproduc- 

 tion are always exserted whether they be male or female. It is not 

 easy to explain why this portion of the shell is differently coloured, 

 unless it is in keeping with what is noticed in the colouring of certain 

 flowers, butterflies, &c. The whole of the Littorince have the aperture 

 of dark colour though highly enamelled, and this whitish line is a 

 conspicuous diversity in the appearance, though it would be a very 

 narrow view of the operations of nature to say that its only purpose 

 was to attract. 



The author also establishes that the Australian Littorinidee so 



* 'Arch. f. Mikr. Anat.,' xxv. (1S78) 341. 

 t ' Proc. Linn. Soc. N.S.W.,' iii. 55. 



VOL. II. 2 D 



