154 THE AMPHIOXUS. 



and a duct, has thus not been formed through out- 

 growth from the place of opening, but has reached its 

 abstraction along its whole length. 



The cells of the club-shaped, thickened glandular 

 portion enlarge, and assume a granular appearance 

 and yellowish colour. The thin duct is composed of 

 a small number of somewhat flat cells, and on that 

 side of these, which is turned towards the lumen of 

 the canal, faint cilia are at once formed. 



Kowalevsky speaks, in his treatise, of two glands, 

 and gives representations of them. He was misled by 

 ^a thickening of the alimentary canal in front of the 

 gland, a ciliated organ, of \vhich we shall speak again 

 later on. 



With regard to the development of this gland, 

 Kowalevsky fell into the extraordinary mistake of 

 supposing that it originated through change of the 

 primitive vertebrae. We have already shown above 

 that the first mesoblastic somite differentiates much 

 earlier in just the same way as those which succeed it, 

 having, at the same time, nothing to do with the 

 formation of this gland. 



