906 ANATOMY AND DEVELOPMENT 



apex of a well-developed white papilla (PI. 47, fig. 4). It is 

 enormously enlarged, and is prolonged forward as a long tubular 

 gland, the structure of which resembles that of the vesicles of 

 the crural glands in the other legs. This gland lies in the 

 lateral compartment of the body cavity, and extends forward to 

 the level of the 9th leg (PI. 48, fig. 8, and PI. 53, fig. 43). It is 

 described by Professor Balfour as the accessory gland of the 

 male, and is seen in section lying immediately dorsal to the 

 nerve-cord in fig. 20, 



PART III. 



THE DEVELOPMENT OF PERIPATUS CAPENSIS. 



[The remarkable discoveries about the early development of 

 Peripatus, which Balfour made in June last, shortly before 

 starting for Switzerland, have already been the subject of a 

 short communication to the Royal Society (Proc. Roy. Soc. 

 No. 222, 1882). They relate (i) to the blastopore, (2) to the 

 origin of the mesoblast. 



Balfour left no manuscript account or notes of his discovery 

 in connection with the drawings which he prepared in order to 

 illustrate it, but he spoke about it to Professor Ray Lankester 

 and also to us, and he further gave a short account of the matter 

 in a private letter to Professor Kleinenberg. 



In this letter, which by the courtesy of Professor Kleinenberg 

 we have been permitted to see, he describes the blastopore as an 

 elongated slit-like structure extending along nearly the whole 

 ventral surface ; and further states, as the result of his examin- 

 ation of the few and ill-preserved embryos in his possession, 

 that the mesoblast appears to originate as paired outgrowths 

 from the lips of the blastopore. 



The drawings left by Balfour in connection with the dis- 

 coveries are four in number: one of the entire embryo, shewing 

 the slit-like blastopore and the mesoblastic somites, the other 

 three depicting the transverse sections of the same embryo. 



