212 SUMMARY OF GUERENT RESEARCHES RELATING TO 



of villous-like processes (" Zottclien,") which Eimer derived from 

 extruded yolk-material. 



Formation of Mesoblast and Persistence of Blastopore in the 

 Lamprey.* — Mr. A. E. Shipley finds that tbe mesenteron of the 

 lamprey is present from the first sign of invagination, and that so 

 far it resembles Am^Moxus and differs from the frog. The mesoblast 

 first appears by the differentiation of two bands of those yolk-cells 

 which lie in the angles formed by the invaginated mesenteron and 

 the epiblast ; at a very much later stage it is completed ventrally by 

 the down-growth on each side of the mesoblastic plates, which 

 proliferate cells at their edge. 



The author agrees with Schultze and Calberla that the blastopore 

 persists as the anus ; as the same phenomenon has been demonstrated 

 for various Amphibia by Miss Johnson (newt), Gasser (Alytes), and 

 Spenser (frog), its persistence in the Cyclostomata leads to the view 

 that it is a primitive feature retained in those eggs which have not 

 become much modified by the presence of a large mass of yolk ; a re- 

 examination of AmpMoxus as to this point would be very instructive. 

 Behind the anus, and at a point corresponding to the front lip of the 

 blastopore, there is a mass of indifferent tissue, into which there pass 

 representatives of all three germinal layers, and which appears to 

 represent the primitive streak. 



Breeding of Salmon from Parents which have never visited 

 the Sea.f — Dr. F. Day reports on experiments made at Howietoun, 

 from which he concludes that (1) male parr and smolts may afford 

 milt competent to fertilize ova, but when from fish of the second 

 season, or up to thirty-two months old, it is (? always) of insufficient 

 strength for strong and vigorous fry to be raised. (2) Female smolts 

 or grilse may give eggs at thirty-two months of age, but those which 

 are a season older are better capable of producing vigorous fry ; for 

 the purpose of developing ova a visit to the sea is not a physiological 

 necessity. (3) Young male Salmonidte are more matured for breeding 

 purposes than are young females of the same age, (4) Although 

 females under twenty-four months of age may give ova, such are of 

 little use for breeding purposes, as the embryos do not become well 

 developed or vigorous, and the young when hatched are frequently 

 malformed. (5) Older Salmonidee, as a rule, give larger ova than 

 younger or smaller ones ; but the size of the egg varies with age and 

 condition. (6) Among the produce of every female fish there may be 

 found variations in the size of the eggs. (7) From larger ova finer 

 and more rapidly growing fry are produced ; consequently races may 

 be improved by the selection of the breeders. 



Hatching the Eggs of Cod.:}: — Mr. J. A. Eyder, after describing 

 a new apparatus for hatching cod's eggs (allowing of a slow up and 

 down movement of the water, which seems to aerate the eggs and give 

 ]3etter results than the usual rapid motion), observes that the larval 



* Proc. Koy. Soc, xxxix. (1885) pp. 244-8. 



t Trans. Linn. Soc, Lond., ii. (1885) pp. 447-68 (2 pla.). 



t Science, vii. (1886) pp. 26-9 (1 fig.). 



