38 PACKING THE TROUT OVA. 



is not grasped by the thumb, or it will break up. The square is 

 then lifted and placed in the top tray, the attendant removing 

 it from the pile to where the trays were first placed, and gently 

 pressing the pad over the eggs, while the operator turns and selects 

 the next one, and so on until all the eggs have been covered. The 

 pile of trays now occupies its first position, ready to receive ova 

 from the next set of frames, which are now placed on the table. 

 As it is evidently impossible to make all the pads of felted moss of 

 exactly the same thickness, it requires much practice and consider- 

 able deh'cacy of touch to ensure all the trays being filled up to 

 exactly the proper height, so that, without any undue pressure 

 on the eggs, they may be sufficiently packed to resist the many 

 contingencies of a railway journey. 



In packing eggs for abroad swan's down cannot be used, because 

 after fifteen or twenty days it becomes so charged with carbonic 

 acid as to partially suffocate the embryos. For American and Con- 

 tinental consignments unbleached lino is therefore substituted. 



But when ova is packed for the antipodes even unbleached lino 

 is undesirable, as, from the length of journey, the eggs are very far 

 advanced on arrival, and it is absolutely necessary to remove the 

 whole of the carbonic acid given off by the embryo. This can only 

 be done by the immediate contact of live moss, and very great 

 practical difficulties now intervene. If the moss is pressed in 

 felting sufficiently to make the pad tolerably adhesive, much of it 

 is crushed, and dies and blanches en route ; if, on the other hand, 

 the pad is so slightly felted as not to crush any sprigs of the moss, 

 it is almost impossible to handle it sufficiently to lift the square 

 after it has received the eggs from the frame into the tray. Per- 

 haps the best plan is to use very thin pads, with a square of 

 unbleached lino between them. In this way a thin pad of moss is 

 thrown from a tray over the frame, a square of lino is then placed 

 over the moss, and the whole reversed on the padded tray. The 

 lino is then lifted in the same manner as the square of swan's down, 

 and placed in the travelling tray ; a very thin pad of moss is then 

 thrown over the eggs in the tray, and another thin pad of moss 

 thrown over the next frame, covered with lino, and the process 

 continued as before. Packed in this way, a section would show : 



