718 SDMMAKY OF CURRENT RESEARCHES RELATING TO 



was observed to take a zigzag coiirsc, but in most cases there were 

 curves ami rings ; the latter might be to the right or to the left, but 

 either direction was constant in any given sniiil. After removal of 

 both suin-a-crsoi)hageal ganglia, the snail was enticed from its shell with 

 difficulty, and soon retired again. Removal of the pedal-visceral 

 ganglia paralysed the animal and it could no longer return to its shell ; 

 it bled profusely and soon died. 



In slur's the effect of removal of a supra-ajsophageal ganglion is the 

 immediate curvature of the body from the opposite side ; the head is 

 applied to the foot, and the animal forms a ring. If it moves it turns 

 from the uninjured towards the injured ganglion, or in the opposite 

 direction to the snail. This difference may be due to the slugs having 

 been examined immediately after the operation had been performed on 

 them. 



Creeping Movements.* — Prof. V. Willem seeks to explain the f icts 

 that fresh-water Gastropods can glide slowly along the surface of the 

 water, with the foot upwards, as if they were creeping along the inferior 

 surface of a horizontal plate of glass ; and that when they do so the 

 motions of the foot are the same as when the animal is moving on a solid 

 surface. After discussing the various explanations which have already 

 been offered. Prof Willem proceeds to give an account of his own 

 observations and experiments. These have led him to conclude that the 

 animal begins by attaching itself to the thin superficial skin which 

 always covers pond-water, and that then it creeps along the inferior 

 surface of a thin coat of mucus secreted by its foot. " This locomotion," 

 he says, " only ditfers from locomotion on solid substances in that here 

 the mollusc has to depend on the rigidity of the train of mucus alone, 

 while in the other case the train of mucus is attached to a solid 

 surface." 



Systematic Position of Hero.f — M. A. Vayssiere has some notes 

 on the organization of this opisthobranch mollusc, whose exact syste- 

 matic position is still a matter of some uncertainty. The dendritic 

 form of the appendage of the edge of the mantle, which has led to the 

 creature being placed with the Dendronotidje, appears to be due to the 

 action of alcohol. In life, however, these appendages are seen to be 

 true dorsal fusiform cirri, which are arranged symmetrically by pedun- 

 culated groups on the lateral parts of the back. They have considerable 

 resemblance to those of Calona Cavolinii, but there are, in addition, on 

 the sides of the cephalic region a pair of tufts, which carry the largest 

 number and the longest of the cirri, the posterior groups having only 

 one, two, or three rudimentary cii-ri. The arrangement of the append- 

 ages shows that Hero is one of the Aeolididao, and this is confirmed by 

 the odontophore. As the radular characters of the species found in the 

 Bay of Marseilles differ from those of H. formosa described by Sars and 

 Bergh, the author regards it as a new species, to which, however, he 

 gives no name. 



Anatomy of Valvata piscinalis. — M. P. Garnault % has investigated 

 the anatomy of this hermaphrodite mollusc. He finds that the renal 

 tube is simple above, but that the greater part is divided by a partition 

 into two secondary tubes. Of these the right communicates with the 



* Bull. Acad. E. Sci. Belg., Ivii. (1888) pp. 421-9. 



t Comptes Readus, evil. (1888) pp. 136-8. J Ibid., cvi. (1888) pp. 1813-15. 



