OF PERIPATUS CAPENSIS. 913 



from development." (Comparative Embryology, Vol. I. p. 378, 

 the original edition 1 .) 



"TRACHEATA. Insecta. It (the mesoblast) grows inwards 

 from the lips of the germinal groove, which probably represents 

 the remains of a blastopore." (Comparative Embryology, Vol. II. 

 p. 291, the original edition 2 .) 



" It is, therefore, highly probable that the paired ingrowths 

 of the mesoblast from the lips of the blastopore may have been, 

 in the first instance, derived from a pair of archenteric diver- 

 ticula." (Comparative Embryology, Vol. II. p. 294, the original 

 edition 3 .) 



The facts now recorded were discovered in June last, only 

 a short time before Balfour started for Switzerland ; we know 

 but little of the new ideas which they called up in his mind. 

 We can only point to passages in his published works which 

 seem to indicate the direction which his speculations would have 

 taken. 



After speculating as to the probability of a genetic connec- 

 tion between the circumoral nervous system of the Ccelenterata, 

 and the nervous system of Echinodermata, Platyelminthes, Chae- 

 topoda, Mollusca, &c., he goes on to say : 



" A circumoral nerve-ring, if longitudinally extended, might 

 give rise to a pair of nerve-cords united in front and behind 

 exactly such a nervous system, in fact, as is present in many 

 Nemertines (the Enopla and Pelagonemertes), in Peripatus and 

 in primitive molluscan types (Chiton, Fissurella, &c.). From 

 the lateral parts of this ring it would be easy to derive the ventral 

 cord of the Chsetopoda and Arthropoda. It is especially de- 

 serving of notice, in connection with the nervous system of the 

 above-mentioned Nemertines and Peripatus, that the commis- 

 sure connecting the two nerve-cords behind is placed on the 

 dorsal side of the intestines. As is at once obvious, by referring 

 to the diagram (fig. 231 B), this is the position this commissure 

 ought, undoubtedly, to occupy if derived from part of a nerve- 

 ring which originally followed more or less closely the ciliated 

 edge of the body of the supposed radiate ancestor." (Compara- 

 tive Embryology, Vol. n. pp. 311, 312, the original edition 4 .) 



1 This edition, Vol. II. p. 457. " This edition, Vol. in. p. 352. 



3 This edition, Vol. in. p. 356. 4 This edition, Vol. in. pp. 378, 379. 



