298 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Structure of Embryonic Supporting Tissue and Origin of Con- 

 nective-tissue Fibrils.* -- F. Meves has studied the chondriosomes 



which he finds in all the cells of the supporting tissue of the embryo, 

 and he brings forward evidence that they form the material for connec- 

 tive-tissue fibrils. He describes the development of tendons, and shows 

 that the fibrils, after they are once formed, increase independently both 

 in length and thickness. 



C. G-eneral. 



Relation between Ciliary and Muscular Movements.! — A. G. 

 Mayer has found that in Scyphornedusae the nervous stimulus which 

 produces each pulsation is caused by the constant formation of a uric 

 oxalate of sodium in the marginal sense-clubs. This sodium oxalate 

 precipitates the calcium which constantly enters the sense-club from the 

 surrounding sea-water, and forms crystals of calcium oxalate, while 

 sodium chloride is set free. Thus the stimulus which produces pulsation 

 is due to ionic sodium. 



The sodium of the sea-water is in many cases (Annelids, barnacles, 

 Ctenophores, medusas) a strong nemo-muscular stimulant, while the 

 magnesium, calcium and potassium are inhibitors, and exactly counter- 

 balance the stimulating effect of the sodium, thus permitting weak 

 internal stimuli to produce movements. 



It is remarkable, however, that the effects of the ions, sodium, 

 magnesium, potassium, and calcium, upon the movements of cilia of 

 Infusoria, vertebrate spermatoza, marine larvae, and Ctenophores, is 

 always the exact opposite of their effect on the neuro-muscular system. 

 In ciliary movement the depressant effect of sodium is offset by the 

 stimulating influence of magnesium, potassium, and calcium. A 

 Spirillum living in fresh-water reacted as do the cilia of animals, and it 

 is suggested that the ciliary movements of animals may have been taken 

 over from motile plant-like ancestors and maintained unchanged, where- 

 as their neuro-muscular movements have been developed later and are 

 controlled by the ions of the blood salts in a manner the exact reverse 

 of cilia. 



Distribution of Chitin.J — D. H. Wester discusses the occurrence of 

 chitin in Arthropods (even in the mid-gut in some cases) ; in Molluscs 

 (e.g. in cuttlefish jaws, snail's radula, some bivalve shells and siphons, 

 as in Mya ; operculum of Buccinam) ; in Chwtopods (setae, tentacles, 

 intestine of earthworm and Aphrodite) ; in Brachiopods (shell, stalk and 

 bristles of Lingula) ; in cuticle of Bryozoa ; in Hydroids ; in the gem- 

 mules of a fresh-water sponge. There is no chitin in silk or in byssus. 

 None was found in the egg-shells of Invertebrates. There is no evidence 

 of chitin in Protozoa, Echinoderma, or Vertebrates. 



Supplementary Function of Foot in Yellow Races. § — Lannelongue 

 brings together a number of interesting cases among yellow races in 



* Arch. Mikr. Anat., lxxv. (1910) pp. 149-208 (2 pis.). 

 t Proc. Soc. Exp. Biol, and Med., vii. O.909) pp. 19-20. 

 J Zool. Jahrb., xxviii. (1910) pp. 531-68 (1 pi. and 1 tig.). 

 § Comptes Rendus, cl. (1910) pp. 503-7. 



