212 SUMMARY OF CURRENT RESEARCHES RELATING TO 



body of Synapta inhserens. When it is separated it moves by means of 

 its well-developed foot. As Malard showed, there is a minute delicate 

 shell incompletely covered by the reflected lobes of the mantle ; the 

 mantle has an anterior pedal opening and a posterior siphon ; the 

 pallial papillae are strongly developed ; the gills have one lamella ; the 

 posterior pallial cavity forms a brood chamber. Anthony finds that the 

 prodissoconch is clearly visible ; that the elastic portion of the ligament 

 is internal ; that there are two adductors, two anterior retractors, and 

 two posterior retractors of the foot ; that the pallial line is without a 

 sinus ; and that the labial palps are very distinct. The genus is nearly 

 allied to Montacuta, but the resemblances to Scioheretia are perhaps due 

 to convergence. 



■■o^ 



structure of Solan.* — Ekendranath Ghosh gives an account of the 

 structure of what seems to be a dwarfed form of SoUn fonesi, from Chilka 

 Lake. The siphon-wall consists of outer columnar cells on a distinct 

 basement membrane ; a thick layer of connective tissue with many elastic- 

 fibres and connective-tissue corpuscles ; a thick longitudinal layer of 

 muscle-fibres, grouped into radial bundles ; a thin layer of connective 

 tissue ; a thin layer of transverse muscle-fibres ; a thin layer of longi- 

 tudinal muscle-fibres ; another thin layer of transverse muscle-fibres ; 

 and a layer of columnar epithelium lining the canals. The digestive, 

 nervous, and excretory systems are described in some detail. 



Arthropoda. 

 o. Insecta. 



Role of Pericardial Cells in Insects. f — A. Ch. Hollande publishes 

 a preliminary paper on the physiological role of the pericardial cells 

 which are disposed, in insects, round the cardiac sinus, and connected 

 with each other and with the sinus by striated muscle-fibres and fine 

 smooth fibrils. There are usually two nuclei in a cell. These cells, 

 which have usually been considered excretory, have the function of 

 absorbing albuminoid substances of alimentary origin, and rendering 

 them assimilable. During metamorphosis the pericardial cells persist 

 without modification, and, with rare exceptions, continue to function by 

 absorbing the albuminoid substances liberated into the blood either as a 

 result of phagocytosis or of the breaking down of larval cells. 



The acid reaction of the pericardial cells is apparently due to the 

 presence of phosphates. The cells are not in any true sense excretory ; 

 they are glandular elements which transform and modify the substances 

 which they absorb, the transformations being due in part to reducing 

 agents acting in an acid medium. Throughout the life of the insect 

 the pericardial cells absorb the oxidized products resulting from the action 

 of the phagocytes, and return them to the blood in a reduced form. 

 Finally, these cells neutralize the alkaline products which arise in the 

 course of metabolism, and render them innocuous. 



♦ Memoirs Indian Museum, v. (1916) pp. 367-74 (3 figs.), 

 t Arch. Exp6r. Zool., Iv. (1916) pp. 67-84. 



