Birds observed hetivcen England and Cape of Good Hope. 193 



the formation of the embryo, and practically that the nuclei 

 of the parablast layer are morphologically functionless. He 

 regards the nuclear material of the parablast as analogous to 

 that in the yolk-pole of a holoblastic ovum, which, under its 

 new conditions, may go on dividing, but which has no longer 

 any part to play. Others, headed by Gensch, have shown, I 

 think without doubt, that the parablast cells play a prominent 

 part in the formation of blood and the connective tissue 

 series, and in fishes the perivitelline circulation is probably 

 of parablastic origin. In the herring, cod, Trachinus, and 

 probably the whole group of pelagic ova, there is, however, 

 no trace of a vitelline circulation, yet cells are produced in 

 the parablast of these forms in the same manner as in the 

 trout. Further, these cells appear quite as early in the 

 herring and similar forms — indeed, apparently earlier in some 

 cases. What, then, can become of these early differentiated 

 cells ? In the cases cited there is no vascular system until 

 a late stage, so they cannot be transformed into blood cor- 

 puscles, yet they most certainly do not undergo degeneration. 

 There thus appears no alternative but that the cells must 

 take part in the formation of the embryo itself. It thus 

 appears that, from a consideration of the physiological func- 

 tion of the parablast, the morphological value of this layer 

 is seen to be more important than has hitherto been admitted. 

 I have purposely omitted here any reference to Kyder's theory 

 of " Yelk-hypoblast," because this has reference only to the 

 absorption of that portion of the food-yolk which remains 

 unassimilated at the time the embryo hatches. 



XVI. Notes on Birds observed on various Voyages between 

 England and the Cape of Good Hope. By Speaeman" 

 SwiNBUiiNE, Esq. (Communicated by J. J. Dalgleish, 

 Esq.) 



(Read 17th Februar)^ 1886.) 



The following is a short account of the different birds seen 

 on a series of voyages from Southampton to Cape Town, 

 extending over a period of two and a half years, from July 



VOL. IX. N 



