212 SUMMARY OF CURRENT RESEARCHES RELATING TO 



provided witli a chitinous triturating apparatus ; tlie commissures con- 

 necting the nerve-centres are excessively short, and the cerebroid 

 ganglia are proportionately large, owing possibly to the complete 

 absence of visceral ganglia. ^ 



Absolute Force of the Adductor Muscles of Lamellibranchs * — 

 F. Plateau has commenced a series of researches on the absolute force 

 of the muscles of invertebrates by an investigation on certain Lamelli- 

 branchs. The name of absolute or static force was given by Weber to 

 the force measured by the weight which exactly equilibrates the con- 

 traction of a muscle ; in other words, if a muscle is fixed by one end, 

 and a weight suspended at the other, the absolute force is measured by 

 the maximum weight which the muscle in action can carry without 

 either elongating or contracting. Hitherto observations seem to have 

 been confined to the frog and to man. 



After a notice of the work of preceding investigators inta the 

 physiology of Lamellibranch muscles, the author points out that in 

 most of this group the adductor muscles may be found to consist of a 

 transparent (generally the largest) and an opaque portion; the latter 

 appears to be formed of smooth, the former of transversely striated 

 fibres. The experiments of Coutance show that in Pectens the two 

 muscular portions have different functions : while the transparent 

 muscle contracts rapidly, the opaque smooth muscle does so slowly. 



Plateau has experimented on twenty different species, but finally 

 limited his researches to Unio pictorum, Cyclas rivicola, Artemis exoleta, 

 Tellina incarnata, and Pandora rostrata. A full account of the modes 

 of experiment is given, together with elaborate tables of the results ; 

 these cannot be reproduced here, and it must suffice to say that it has 

 been found that the only way of usefully comparing the muscular force 

 of Lamellibranchs with that of the higher animals is to discover the 

 absolute force of the muscles for each square centimetre of transverse 

 section. When the comparison is thus made it is found that the 

 absolute force of the adductors of Lamellibranchs is analogous to that 

 of vertebrates. To the objection that moUuscan muscles are smooth, 

 and that vertebrate muscles are transversely striated, the only possible 

 answer at this moment is that the author has also made some inves- 

 tigations on the muscular force of Crustacea, which will shortly be 

 published and in which he hopes to explain the apparent anomaly. 



Water-pores of the Lamellibranch Foot. — H. Griesbach has main- 

 tained f the existence oi pori aquiferi in the Lamellibranch foot, while 

 J. Carriere held J the contrary view. J. T. Cattie § has studied 

 a considerable number of species, and does not find the least trace of 

 aquiferous pore ; and T. Barrois || arrives at the same results. He 

 discusses the work of Carriere and himself, and finds that they have 

 studied most of the forms where the presence of aquiferous pores has 



* Bull. Acad. R. Sci. Belg., vi. (1883) pp. 226-59 (1 pi.), 

 t See this Journal, iii. (1883) p. 353. 

 t Ibid., p. 639. 



§ Zool. Anzeig., vi. (1883) pp. 560-2. 



II " Private imprint from Lille, dated October 30th, 1883." Cf. Science, iii. 

 (1884) pp. 130-1. 



