ZOOLOGY AND BOTANY, MIOEOSCOPY, ETC. 53 



pleted MSS., and drawings, which it is intended to publish in the 

 ' Quarterly Journal of Microscopical Science ' for April. His dis- 

 coveries, however, on the early embryology of P. capensis are so 

 interesting that a preliminary note has been communicated to the 

 Eoyal Society. 



The results are shortly as follows : — That a widely-open slit-like 

 blastopore is formed in the early oval embryo, which blastopore, 

 occupying the median ventral line, becomes closed in its centre, an 

 anterior portion remaining open as a mouth, whilst a posterior portion 

 apparently becomes the anus. The mesoblast is formed from the 

 hypoblast at the lips of the blastopore, and makes its appearance as a 

 series of paired hollow outgrowths from the cavity of the archenteron. 

 This most primitive method of the formation of the mesoblastic 

 somites, closely similar to that occurring in Amphioxus and other 

 ancestral forms, is of the greatest morphological significance, and it 

 is especially interesting to find that it survives in an entirely un- 

 modified condition in Peripatus, the adult organization of which 

 proves that it is a representative of an animal stock of the most 

 remote antiquity. 



Mr. A. Sedgwick, by examining some embryos in Prof. Balfour's 

 collection of material as yet uninvestigated, has been able to confirm 

 his results, and also by finding earlier stages to verify certain points 

 in the developmental history which rested, at the stage at which 

 Prof, Balfour's inquiry ceased, mainly on inference. 



In the discussion which took place on the paper, Mr. Sedgwick 

 pointed out the close resemblance of the early embryo Peripatus with 

 open blastopore to an Actinia, the mesoblastic pouches corresponding 

 to intermesenterial cavities, and the blastopore to the mouth, and 

 urged that the discovery tended to confirm Prof. Balfour's published 

 theory as to the origin of the bilateralia from the elongation trans- 

 versely of a disk-like ancestor, the ventral nerve-cords having been 

 formed by the pulling out into long loops of a circumoral ring. 

 Prof. Lankester considered that the view that the blastopore represents 

 a structure which in an ancestral form acted as a mouth, must be 

 abandoned. The blastopore is very probably merely an aperture 

 necessarily formed in the process of production of the hypoblast by 

 invagination, and has never had any special function. Prof. Huxley 

 also pointed out the essential difference between the peripheral nerve- 

 ring of Hydromedus8e and a true circumoral nerve-ring. 



Formation of Prussia Acid in a Myriopod.* — A foreign Myriopod 

 occurring in hothouses in Holland, and identified as belonging to the 

 genus Fontaria, has the power of secreting this substance. Attention 

 was called to this animal by its emitting a distinct odour of oil of 

 bitter almonds when excited ; the odour is especially apparent when it 

 is crushed. Maceration of specimens in water showed at once that the 

 smell was due to this acid, it being detected in the water. A series 

 of experiments have been made by C. Guldensteeden-Egeling to test 



* Pflliger's Arch. f. Physiologie, xxviii. p. 576. Cf. Natuiforscher, xv. (1882) 

 p. 433. 



