402 NOTES AND MEMORANDA, 



closely resemble the European genus Litforina, that they cannot be 

 generically separated from it ; that the genus Bisella should be sup- 

 pressed as no permanent generic character can be defined in it ; that 

 Tedaria pijramidalis is merely Littorina with a double line of granules, 

 and that all the Australian species have the groove or line above 

 mentioned, which is in some way connected with the organs of repro- 

 duction. 



Structure and Physiology of the Octopus. — An extended series 

 of observations made on this animal at Roscoff are published by the 

 Royal Academy of Belgium.* Attention has been already drawn in 

 this journal (pp. 164-166) to the new substance which M. Fredericq 

 has found in the blood and to the action of the chromatophores ; we 

 may now add an accoimt of the vascular, excretory, and other systems. 



Circulator y Organs. — Examined under water, and after the removal 

 of a small portion of the ventral wall of the mantle and of the visceral 

 sac, the rhythm of the heart is easily observed ; the contraction com- 

 mences in the peritoneal vessels and vena cava, and passes onwards to 

 the " venous hearts " at the base of the branchire, thence to the 

 auricles, and thence to the arterial ventricle or heart proper. About 

 thirty-five pulsations can be counted per minute, and as each takes 

 about ^V of a minute the contractions overlap more or less. The 

 action of this organ is not atfected by the removal of the peri- 

 cesophageal ganglion, the section of the pallial nerves, or the extirpation 

 of the pallial ganglia, and this evidence on the one hand, as well as 

 the fact that different parts removed from the organism, or the whole 

 heart removed from water, still continue to beat for a time, point 

 to the presence of exciting centres in the cardiac region itself. The 

 contact of the air, mechanical, and still more electrical excitation, 

 accelerate the action of the heart, on which also certain nerves from 

 the cesophageal collar seem to have an accelerating or a depressing 

 action ; the former run ah>ng the great vena cava, and the moderator 

 fibres are found in the trunks of the visceral nerves, as was first shown 

 by Paul Bert. 



The latter seem to resemble very closely the pneumogastric 

 nerves of the Vertelrata, inasmuch as section of them increases the 

 number of pulsations, while weak excitation diminishes them, and 

 strong excitation brings the heart to a standstill in diastole. 



But rhythmical contractility is not confined to the heart and its 

 neighbouring vessels ; the veins, even in their furthest ramifications, 

 present the same character, as may be well seen by examining an 

 Octopus into which a little colouring matter has been introduced ; two 

 large veins may then be seen in any one of the arms, which anasto- 

 mose largely with a number of smaller subcutaneous venous ramules ; 

 along their whole length a wave of contraction may be seen to pass, 

 which, though apparently irregular for the whole, is quite regular and 

 rhythmical in any given portion ; these beats are altogether inde- 

 pendent of the central nervous system. 



The pressure of the blood in the arteries appears to be very great, 



* ' Bull. Aca.l. Roy. Belg.,' xlvi. (1878) 710. 



