106 F. M, BALFOUR. 



Postscript to the Paper on the Development of the 

 Araneina 



Since the publication of the preceding paper, my attention 

 has been called to a very important paper by Salensky, on the 

 " Development of the Araneina/^ written in Eussian^ which ap- 

 peared in 1871 in the 'Kiew Society of Naturalists/ An abstract 

 of this paper is published in Hofmann and Schwalbe's ' Jahresber- 

 ichte ' for 1878. From the abstract it appears that Salensky was 

 able to carry his investigations a good deal further than previous 

 investigators. He detected the nuclei in the yolk, and showed that 

 they gave rise in part to the inner layer of blastoderm cells. He 

 further showed that the mesoblast became split into splanchnic 

 and somatic layers, and gave an account of the development of 

 the heart, similar to that in my paper. He believes that the 

 third and fourth pairs of provisional abdominal appendages be- 

 come the spinning mammillae ; while the anterior pair gives rise 

 to the pulmonary sacs. I was myself unable to follow in detail 

 the disappearance of the four provisional appendages, though 

 from various considerations I was led to reject the view that 

 the third and fourth pairs became the spinning mammillae. I 

 could not moreover trace the development of the pulmonary sacs 

 from the first pair of abdominal appendages. Further ob- 

 servation on these points with fresh material are much required ; 

 and I hope myself, to be able before long, to return to this part 

 of the development as well as to the history of the later stages. 



