St. Andrews Marine Lahoratory. 91 



mulberry stage. The blastoderm had made considerable 

 progress on the 19th, and on the 20th February, at 3 p.m., 

 when they reached the Marine Laboratory here, the blasto- 

 pore had closed and eight or nine muscle-plates had formed. 

 Kupfier's vesicle was present in some. Many of the embryos 

 showed minute black specks along the body, and in one a 

 black chromatophore occurred in each eye. The yolk presented 

 a slightly wavy aspect, which was rendered evident by careful 

 adjustment of the focus ; and the same feature was noticed in 

 the examples of last year. The eggs are extremely buoyant, 

 and measure 1"1430 millim., a size wliich exactly corresponds 

 with the empty capsules formerly alluded to, but it is con- 

 siderably larger than those sent last year from Shetland. 



Next day (21st February), at 4 P.M., the black pigment in 

 some was more distinct along the body, being grouped chiefly 

 at the sides, yet in front a few specks invaded the median 

 region behind the eyes. In others, however, the pigment 

 occurred posteriorly over the body generally. Though the tail 

 was somewhat longer than in the figure of last year *, the 

 muscle-plates were less distinct. The alar expansion was little 

 marked, except in the pectoral region. An abnormal e.gg 

 showed a deviation of the notochord to the right, and 

 Kupflfer's vesicle was also on one side of the median line. 

 On the 22nd February all the organs were more clearly 

 outlined, the muscle-plates were more numerous, the lenses 

 more distinct, and the pigment dotted all over the body. The 

 early condition of the auditory organs in this form is inter- 

 esting ; and, in addition to what is given in the "Researches" f, 

 it may be stated that in the green cod, after the solid thick- 

 ening of the sensory layer of the epiblast has formed, the 

 lumen, instead of being spherical, is elongated antero-poste- 

 riorly, the slit being somewhat spindle-shaped. No cellular 

 elements in the auditory cysts can be made out in the living 

 forms — probably from the extreme delicacy and transparency 

 of the tissues. Kupffer's vesicle is still present in some. 

 A solid longitudinal bar occurs in the region of the heart 

 and a curved transverse line behind it. The comparative 

 narrowness of the body of the embryo is a feature at this 

 stage. The temperature at this time was low, so that develop- 

 ment went on slowly. On the 23rd February the tail 

 extended further round the yolk, which, moreover, had a 

 peculiar oleaginous aspect, occasionally with a few streaks 

 in its substance, and it was not much diminished. The noto- 



* Eleventh Ann. Kept. Fishery Board for Scotland, pi. ix. fig. 2. 

 t M'Intosh and Prince, Trans. Roy. Soc. Edinb. vol. xxxv, pt. iii. 

 pp. 760 and 761 (1890). 



