314 SUMMARY OF CURRENT RESEARCHES RELATING TO 



motor apparatus. On every chromatophore may be distinguished a 

 peculiar pigment-body and a number of radial fibres issuing from it. 

 There is a diversity of opinion as to whether the pigment-body is 

 unicellular or multicellular. Both Chun and Steinach found that the 

 radial fibres, often anastomosing, occasionally pass directly over into the 

 skin musculature. Chun found in Bolitama that there is a connection 

 between one (and of ten several) of the radial fibres and fine side-branches 

 of the skin-nerves. Numerous observations on the physiology of the 

 chroinatophores are quoted, but at present unification of the results 

 seems difficult. 



3. Gastropoda. 



Hermaphroditism in a Chiton.* — Harold Heath has found that 

 Trachydermon raymondi is normally hermaphrodite. In the early stages 

 ova appear in typical fashion ; when the animal becomes half-grown 

 (4-5 mm. long) some of the primitive sex-cells form clusters of sper- 

 matozoa. In 1851 Middendorf reported hermaphroditism in Amicula 

 pallasi, but Plate, in 1899, failed to confirm this, and thought that 

 Middendorf has misinterpreted sperm mother-cells as immature ova. 

 With this single and doubtful exception, all known Chitons have been 

 reported as dioecious, but Heath has shown that Trachydermon raymondi 

 is an indubitable exception. 



The number of spermatozoa is always comparatively small, and they 

 are seemingly shed almost continuously during tlie winter and spring. 

 A number occur grouped together during the breeding season, so that 

 a large number of spermatozoa is not so essential as with the majority 

 of species. The young are brooded over by the parent as in Chiton 

 poli, Ischnochiton imitator, and a few other species. 



The gonad seems to arise as two proliferations of cells of the 

 anterior pericardial wall, and each gonoduct seems to be almost wholly 

 an outgrowth of the wall of the gonad, and not in large measure an 

 ectodermal product. 



Sugar-reducing Power in Helix pomatia.f — Mile. Bellion finds 

 that the liver, albumen-gland, and muscles of Helix jjomatia contain 

 substances which have a sugar-reducing property, and that in the period 

 of activity following hibernation these substances are considerably 

 diminished. This diminution is particularly marked in the liver. 



Pedal Waves of Reptant Molluscs.! — F. Vies finds that there are 

 several interesting varieties in the type of wave-motion to be seen on 

 the foot of creeping Molluscs. These are classified, first, as direct, i.e. 

 those in which the waves are propagated in the same direction as that in 

 which the animal is moving ; and retrograde, where the waves move in 

 an opposite direction, i.e. from front to back. The direct forms are 

 further sub-divided as follows : — monotaxic, with one or more waves 

 visible traversing the whole width of the foot, e.g. Helix, Li max, Arion ; 

 ditaxic, having two systems of waves, each occupying one-half of the 



* Zool. Anzeig., xxxii. (1907) pp. 10-12. 



+ C.R. Soc. Biol. Paris, lxiii. (1907) pp. 238-40. 



X Comptes Rendus, cxlv. (1907) pp. 276-8. 



