32 SALMONID^ OP BRITAIN. 



travelling,* thus some trout were spa'svned at Howietoun on November 27tli, 

 1884, the eggs were at onco packed in a cigar box between layers of muslin in 

 damp moss and sent by train to Cheltenham, arrived the afternoon of the '28th, 

 after experiencing very rough usage on their way, the box even being broken ; 

 still they hatched satisfactoiily, and there was not a single monstrosity. The nest 

 year, on November the 2Gth, some salmon eggs were obtained in the Teith, and 

 also some trout eggs from Howietoun fish, but were not packed sufficiently early 

 to reach me before starting for the train on the 27th. They were sent by train 

 on the 28th, and arrived at Cheltenham on the 29th, about three days after they 

 had been obtained from the fish, but all died, doubtless owing to the shaking 

 they had sustained at this period, or while segmentation was in progress. f 



It is dangerous to the existence of the embryo within the egg to permit them to 

 travel subsequent to the first twenty-four or forty-eight hours after they have 

 been removed from the fish, unless a swing can is employed or some contrivance 

 to prevent shocks, for such interfei-e with the vital processes which are going on 

 and usually occasion its death. It is not in fact until the ova are " eyed," as it 

 is termed by fish-culturists, that they can travel in safety except certain precautions 

 are observed. Tliis eyed period commences somewhere about the fortieth day of 

 incubation in trout eggs, when the outline of the fisli, also the eyes, are visible. 



The appearances presented by salmonoid eggs have been already described, 

 but certain changes may take place owing to morbid conditions. It is very 

 common to observe large or otherwise abnormal ova, some of which are popu- 

 larly termed " wind eggs," passed from a fish among the first which are extruded, 

 Avhile there are often some small hard white and opaque ones that have remained 

 attached to the ovaries or in the abdominal cavity from the previous season. 

 IJnimpregnated eggs when left unmoved in hatching trays mostly continue clear, 

 but concussion may cause them to assume the white and opaque appearance of 

 dead ova. In salt watei' fertile eggs which die become clear in the shell and the 

 embryo contracted in size is visible within, but if in this condition it is transferred 



* At Hnningue eyed ova were first sent in the following manner : a thiu layer of damp moss 

 \Yas placed inside a wide-mouthed bottle and pressed iovm to the bottom, then a layer of eggs, 

 next one of moss and so on up to the top of the shoulder of the bottle, its neck was then filled 

 with damp moss and a paper cover full of holes to admit air, tied over the top. One or more 

 bottles were then jjacked in a box with damp moss, whUe this box was placed in an outer wooden 

 case which was also lined with damp moss. In warm weather ice was added. 



t Mr. Brooks, f.l.s., has kindly furnished the following note on the development of the 

 embryo. " 1. The contents of the egg envelope essentially consist of two portions, a comparatively 

 small quantity of living protoplasm and a large quantity of food-yelk, to be drawn on as required. 

 2. A comparatively thin but continuous film of protoplasm surrounding the whole of the yelk. 

 As the yelk is immediately coagulated when in contact with water the supposition is that the 

 film-like sheet of protoplasm jirevents coagulation. 3. Five or six hours after fertilization the 

 bulk of the germinal protoplasm collects at one pole of the egg forming a lens-shaped mound, 

 the blastoderm, which thins off at the pariphery and is continuous with that portion which 

 envelopes the yelk. 4. During the formation of the blastoderm and prior to its subdivision, its 

 surface is irregular and shows amctboid movements. 5. The blastoderm then becomes divided 

 into two nearly equal parts by a vertical furrow : a few hours later a second is formed at right 

 angles to the first, so that the blastoderm now consists of four segments. 6. Next follow stages, 

 usually during the second day, in which there are eight or sixteen segments but slight irregu- 

 larities are frequent. 7. During the succeedmg days these subdivisions are continued until at 

 the end of a week the blastoderm consists of a cap-like mass of small cells, known as the 

 mulberry mass or monUar. 8. The bastoderm uow consists of a circular plano-convex mass of 

 small cells at one pole of the egg. During the second week this disc begins to spread out over 

 the yelk, thinning out near the centre. 9. About the 15th or 10th day when the blastoderm 

 envelopes about a quarter of the yelk, a thickening appears near one point iai the margin, which 

 is soon recognizable by its opacity and constitutes the first trace of the embryo. It extends 

 inwards as a somewhat triangular streak and increases in length and importance during the next 

 f 2W days. The posterior portion of this streak is where the tail of the future embryo grows free 

 f.'om the yelk, while the anterior part soon becomes raised from the blastoderm and forms the 

 head. 10. With the formation of this more opaque and thickened streak the axis of the embryo 

 can be recognized. The extension of the blastoderm over the yelk continues, but progi-esses more 

 rapidly from the anterior than from the posterior margin. About the end of the third week the 

 yelk is almost entirely enveloped by the blastoderm, the last trace of yelk being seen as a circular 

 spot a little below the posterior end of the embryo. This in turn also becomes closed in by the 

 growth of the blastoderm over it." 



