( l'O ) 



Whether bluud is also i'urmed in the phaeenla of oilier mammals 

 must be carefully looked into. Corpuscles are figured, mixed up 

 with maternal blood-corpuscles, by Nolf for the bat's placenta, by 

 Maximow for that of the rabbit, by Siegenbeek van Heukelom 

 for that of man, with which I feel inclined to identity my „haema- 

 togonia" and of which the first and last-named author decidedly state 

 that they are distinguished by certain characters from polynuclear 

 leucocytes. 



Neither of them, however, refers what he has observed to hae- 

 matopoeisis. 



In point of fact Masquelin and S^vaen (1880) and Frommel (1888) 

 have already stated that blood is formed in the placenta respectively 

 in the rabbit and in the bat. Their observations have up to now 

 convinced but few and do not correspond in their details with m\ 

 own. AYhat I have myself observed in the rabbit, the hedgehog, the 

 shrew and the mole has never emboldened me to conclude to the 

 existence of haematopoietic processes in the placenta: it was not 

 until I had examined the Tarsius-placenta in which the phenomena 

 are so extraordinarily lucid that I was forced to draw the con- 

 clusions of which a rapid sketch was given above, but which is in 

 no way meant to be a generalisation. Ungulates and Lemurs, 

 certain Edentates (and probably also the Cetacea) undoubtedly miss 

 a similar haematopoiesis. Its strong development in Tarsius is 

 perhaps connected with the unfavourable relation in which the small 

 and delicate mother finds itself placed with respect to the compara- 

 tively large foetus, while moreover each parturition is generally 

 immediately followed by a new pregnancy, a circumstance which 

 however exhausting its effect may be upon the mother is decidedly 

 most favourable to the collector of embryologieal material. 



This short account will soon be followed by a full description 

 with plates and figures, which Avill appear in the Report of the 

 Zoological Congress that was held at Cambridge in 1898. 



A discussion followed in which I'rof. Mac Gillavry and Prof. 

 HunKKCHï took part. 



Botany. — „0/t a Contayium vlvain fluidiim caiisin<j the Spot- 

 disease of the Tobacco-leaves". By Prof. M. W. Beijekikck. 



Thg spot-disease of the tobacco plant, also called mosaic-disease, 

 consists in a discoloration of the chlorophyll, spreading in little 

 spots over the leaf and afterwards succeeded by the partly or entirely 

 dying away of the tissue which originally composed the spots. Com- 



