52 SUMMABY OF CURRENT RESEARCHES BELATINa TO 



fate of the accessory body is the same in both Arion and Helix, and the 

 observations which have repeatedly credited it as the origin of 

 different portions of the spermatozoon, are due to its losing at a 

 certain stage its strongly refracting character and becoming invisible, 

 except under very high powers. Platner ascribes no function whatever 

 to the accessory body. The second half of the paper consists of a 

 critical review. 



Movement of the Foot in Lamellibranchs.* — Dr. A. Meischmann 

 comes to the conclusion that the "pori aquiferi" in the feet of 

 Lamellibranchs are either the orifices of glands or artefacts ; this 

 being so, they cannot serve as a means of communication between the 

 blood-vascular system and the surrounding water ; such streams of 

 water as are seen on contraction are not normal vital phenomena, 

 but are pathological. Even if there were pores, they could not, for 

 mechanical reasons, have the functions that have been ascribed to 

 them. The swelling of the foot is due to the entrance of a certain 

 quantity of blood, which, during repose, is stored up in the pallial 

 reservoirs ; the blood is aided by the closure of a strong valve 

 and by the simultaneous relaxation of the musculature of the foot, 

 the lacunae of which become filled by blood. When the foot under- 

 goes erection there is no change of volume of the whole animal, but 

 only a change in the volume of separate parts due to the dislocation 

 of the blood. It has not been proved that water is taken up by the 

 kidneys or intercellular ducts. The Lamellibranchs do not need to 

 take in water. "What is true of them is true also of other groups 

 of molluscs. 



Resting-position of Oysters. t — Dr. K. Mobius refers to a letter 

 by Mr. J. T. Cunningham, wherein the opinion was expressed that 

 oysters rested on the clean right, and not on the left, valve. Out of 

 140 shells examined by Dr. Mobius, only a very few had any foreign 

 organism on the right valve, whilst the rest had sponges, hydroids, 

 &c., on the left valve. Forty-three of these bore on their left valve 

 the body to which the spawn fixed itself. The bottom of an oyster- 

 bed formed by old oyster-shells is not smooth : the young ones 

 being fixed obliquely, the right valve may sometimes be protected 

 so that embryos of other organisms, e.g. sponges, cirripedes, &c., 

 may attach themselves and grow. 



Green Oysters.J — Prof. E. Eay Lankester discusses the cause of 

 the green colour of the gills and labial tentacles of " green oysters," 

 or " huitres de Marennes," which, as Gaillon observed sixty-five years 

 ago, have associated with them in the same waters Navicula ostrearia, 

 and that where there is no such diatom there is no greening. The 

 belief that the green colour is due to copper is discussed, and an 

 account is given of cases where purveyors of oysters have so coloured 

 them. 



Navicula ostrearia contains a light-blue pigment, which it is 



* Zeitschr. f. Wiss. ZooL, xli. (1885) pp. 367-431. 



t Nature, xxxiii. (1885) p. 52. 



X Quart. Journ. Micr. Sci., xxvi. (1885) pp. 71-94 (1 pL). 



