70-i EEPOKT— 1888. 



edge of the Uastoderm, later chiefly at the sides of the embryo. There is a single 

 layer of separate vitelline masses, at tirst beneath the blastoderm, later forming a 

 superficial layer over the whole yolk. 



Neither the Solea, sp. A, nor Solea, sp. B, of RafFaele (' ^Mitt. Zool. Stat. Neapel/ 

 Bd. yiii.) is the ovum of Solea vulgaris. 



The ovum of Solea varieyata has a diameter of 1'36 mm. The oil-globules are 

 separate and not united in groups, and they are larger than in Solea vulgaris; 

 otherwise the ova of the two species are similar. No. 1 of Raffaeles 'specie 

 indeterminate ' is probably the ovum of Solea variegaf.a. 



The ovum of Pleuronectes microcephalus has a diameter of 1'36 to 1'37 mm. 

 The yolk is perfectly homogeneous, the perivitelline space small. The larva, which 

 hatches in seven, eight, or nine days, has a multicolumnar notocliord, the mouth 

 not open, the rectum in contact with the yolk. Ghromatophores, black and yellow 

 in colour, are present over the sides of the body, in the median fin fold, and on the 

 surface of the yolk. 



The ovum of the mackerel is 1'22 mm. in diameter ; the perivitelline space is 

 small ; the yolk has a single large oil-globule, which is at first movable, but after- 

 wards fixed beneath the posterior end of the embryo. Black chromatophores 

 develop on the body of the embryo and on the deeper surface of the oil-globule, 

 and others of a green colour behind the eye and on the side of the embryo above 

 the oil-globule. 



It was suggested that there is a close connection between the presence of one 

 or more oil-globules in a pelagic ovum and the abundance of oil in the body of the 

 parent. The pilchard is oily, and its ovum has an oil-globule ; the herring is less 

 oily, and its ovum is without that structure. 



It was argued that the space round the heart is a part of the body cavity, con- 

 tinuous posteriorly with the lateral body cavities ; while the space between the 

 yolk-sac and the yolk, with which the heart is in open communication, corresponds 

 to the vitelline veins in those Teleostean ova where the latter exist. This venous 

 space seems to be the segmentation cavity continued and remaining open through- 

 out development ; at the same time the cavity has been altered morphologically 

 when the heart develops by the appearance of mesoblastic cells on the surface of 

 the periblast, these cells being the dendritic chromatophores on the surface of the 

 yolk visible in the living larva, but not to be traced in transverse sections. Thus 

 Ryder (' U.S. Fish Commissioners' Report ' for 1882) was wrong in calling the 

 space round the heart the pericardium, and the venous space both segmentation 

 cavity and body cavity ; while Shipley (' Quart. Journ. Mic. Sci.' 1887) gives an 

 account of the parts in Fetromyzon which closely agrees with the above descrip- 

 tion of them in Teleostei, the differences being that he found, no mesoblastic cells 

 on the surface of the yolk in Tetronnjzon, and found that the coelem had not de- 

 veloped in the lateral mesoblast posterior to the heart at the time that it had 

 developed an anterior ventral portion around that organ. 



FRIDAY, SEPTE^IBER 7. 



The following Papers were read : — 



Physiological Depaetment. 



1. On the Physiological Bearing of Waist-belts and Stays. 

 By Professor Rot, M.D., F.li.S., and J, G. Adami, M.A. 



In the course of an investigation upon the work of the heart in health and in 

 disease, certain facts were observed by the authors which throw not a little light 

 upon the physiological bearing of waist-belts and girdles. By means of an instru- 

 ment devised by them — a Cardiometer — they have been enabled to register very 



