334 s. HATTA : 



sliowiDg no structural alteration. Mitotic figures are met witli 

 not infrequently in that part of the epiblast (fig. 54, a-) ; their 

 axis lies, however, in all the cases examined parallel to the 

 plane of the epiblast, giving us an impression of the resulting 

 cells contributing to the formation of no other part than the epi- 

 blast itself; on the contrary, within the structure of the tubule 

 the cells are rapidly multiplying (figs, ol, pt.l and fig. »54, 

 j)t.2), showing that the growth of the tubule is actively going 

 on. In fact, the connection, or rather the intimate contact, of 

 the pronephric tubule with the epiblast is a temporary con- 

 dition ; the separation follows immediately afterwards, and the 

 tubule returns soon into a state similar to that seen in fig. 52 

 {pL2). 



According to Rickert ('88), a similar case is observed 

 in Selachian embryos : the tubules become connected secondarily 

 with the epiblast — what caused him to believe that the latter might 

 give some constituent elements to the tubules. 



The third section behind that represented in fig, 54 (fig. bb) 

 shows, on the right side, the fourth iptA) and, on the left, the third 

 tubule (p^.5) respectively. The latter is not so far developed 

 as its counterpart on the opposite side (fig, 53, pt.3), while the 

 former presents a great progress: it consists of a definite epithel- 

 ium and contains a distinct cavity of triangular shape, although 

 the corresponding tubule on the opposite side (fig, 6ß, pt.4) 

 which is found in the third section behind the last, is much less 

 advanced in development. The fifth tubule, the tubule on the 

 right side of fig. 56 (pt.ô), is somewhat more developed than that 

 which belongs to the anterior somite (the fourth tubule on the 

 opposite side) ; but it has a feature much resembling the fourth 

 tubule on the same side (fig. 55, pL4) and the second on the 



