854 RECORD OF CURRENT RESEARCHES RELATING TO 



Scliiffs late experiments on the so-called motor centres of the brain 

 have led him to believe that it is possible to destroy or to weaken the 

 tactile sensations or the sensations of pressure and of pain by eflfcctiug 

 a lesion of the cerebral substance ; what happens when, after such an 

 experiment, an extremity has its superior portion brought under the 

 influence of the magnetic coil ? When the circuit remains open the 

 effect is nil, but when the circuit is closed then there is seen a very 

 evident increase in the sensibility of the parts, without, however, any 

 consciousness ; the reflex activity is merely more energetic in some 

 portion of the centre which lies inferiorly to that in which stimulation 

 of nerve-centres leads to consciousness. The paper concludes with 

 the following observation : — In hysterical patients, and in the case 

 of those who are suffering from certain other cerebral affections, 

 there is not, so far as any evidence shows, any organ wanting ; at 

 the same time we may admit that there is in them a greater resist- 

 ance than ordinary to the transmission of stimuli to the centre. 

 When the impulse becomes greater it may overcome the resistance 

 and force a transmission of the stimulus. In the dogs experimented on 

 this " forced transmission " may obtain also, but in them it has no 

 effect, inasmuch as it is stopped by the cicatrix of the previously 

 effected lesion. 



M. Schiff promises to continue his observations on the effect of 

 magnetization. 



Mollusca. 



Habits of the Octopus.* — This creature, M. Fredericq tells us, 

 lives alone under large stones, in a kind of hole, the entrance to 

 which is paved with smaller pieces of rock. Its habit of casting 

 all around its retreat what it has left of its repasts betrays its habi- 

 tation, so that when we meet with scattered fragments of crustacean 

 carapaces and molluscan shells, still retaining their ligament, we may 

 be almost certain that an octopus is near. When its home has been 

 discovered it must be withdrawn from it by force; at the moment it is 

 seized it often emits an inky stream of water, but there is not much 

 danger of being bitten ; M. Fredericq in all his experience having 

 been only bitten once, and then quite slightly. If they are well 

 supplied with water and placed in a sufiiciently large aquarium they 

 retain perfect health ; they do not seem to mind captivity, and do not 

 attempt to escape. 



Segmentation of the Ovum in Helix aspersa.f— Professor Perez 

 points out that a large number of observers have agreed with Semper 

 in stating that the follicles of the hermaphrodite gland, previous to 

 the period of functional activity, are clothed with a " vibratile epi- 

 thelium," of which some cells become, later on, converted into ova and 

 others into spermatic cells, and he further shows that Ludwig has 

 correlated the contradictory statements as to the presence or absence 

 of a vitelline membrane, by pointing out that there are in various 

 Pulmonate Gasteropoda all degrees of transition between a superficial 



* ' Arch. Zool. Exper.' (Lacaze-Duthiers), vii. (1878) p. 536. 

 t ' Joui-D. Anat. et Phys.' (Robiu), xv. (1879) p. 329. 



