ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 561 



addition to the paraganglia themselves, isolated groups of chromaffine 

 cells, or single cells, occur in the sympathetic trunks. Further, the 

 suprarenal bodies of Selachians, the cell-nests of Amphibia, the groups 

 of brown cells in Keptiles, are all to be regarded as paraganglia. The 

 thickening of the wall of the internal carotid in mammalian embryos, 

 a thickening often interpenetrated by blood-vessels, and the carotid 

 labyrinth in Amphibia, have nothing to do with paraganglia. 



Development of Adrenal Bodies.* — Dr. Otto Aichel has investigated 

 the development of these structures throughout the vertebrate phylum, 

 with a view to the determination of the homologies of their various 

 elements. He finds that they are universally present above cyclostomes, 

 but finds nothing to support the current view that the suprarenals of 

 the lower vertebrates, like the medulla of the adrenals in the higher, 

 originate from the sympathetic. His results, on the other hand, show 

 that the interrenals of the lower vertebrates, like the adrenals of the 

 higher, originate from the funnels of the mesonephros. The suprarenals 

 of the lower vertebrates arise from the transverse canals of the meso- 

 nephros, as do the adrenals found in the broad ligament in the female 

 of higher vertebrates and the spermatic cord in the male (accessory 

 adrenals). In consequence, in the whole vertebrate series two separate 

 adrenal systems occur. The one is represented by the adrenals of the 

 higher vertebrates and the interrenals of the lower ; the other is repre- 

 sented by the accessory adrenals in the higher vertebrates and the 

 suprarenals in the lower. These accessory adrenals (Marchand's adre- 

 nals) the author finds to be universally present in the higher vertebrates, 

 though often minute, and they are not to be confused with the so-called 

 accessory adrenals which occasionally occur as the result of the dis- 

 memberment of the true adrenal body — a phenomenon analogous to the 

 not infrequent dismemberment of salivary glands, spleen, &c. The 

 differences between higher and lower vertebrates the author explains as 

 follows. In the lower the mesonephros retains throughout life its 

 excretory function, and its two parts (funnels and transverse canals) 

 give rise respectively to interrenals and suprarenals which are equivalent 

 structures. The interrenals are originally paired, but later become 

 unpaired. In the higher vertebrates the mesonephros has only a 

 temporary excretory significance, and though suprarenal bodies originate 

 from its transverse canals as in Selachians, yet these never reach full 

 development, and become the rudimentary accessory adrenals. The 

 interrenals originate in the same manner as in Selachians, remain 

 paired throughout life, and form the obvious adrenals of the higher 

 vertebrates. 



Development of the Duodenal Papillae."] - — Dr. Konrad K. Helly has 

 investigated the development of the primordia of the pancreas, and of 

 the duodenal papillse on which the pancreatic and bile-ducts open in 

 human embryos, in order to determine the reason of the variations 

 in size of the papillas during development. He finds that the portion 

 of pancreatic tissue found in the papilla minor in the adult appears at a 

 very early stage in the embryo, before the appearance of the papilla 



* Arch. Mikr. Anat., lvi. (1900) pp. 1-80 (3 pis. and 1 fig.), 

 t Tom. cit., pp. 291-308 (1 pi. and 12 figs.). 



