1896. THE STRUCTURE OF THE GRAPTOLITES. 



24-5 



observed. This was that the newly-formed budding individual, when 

 at about the same stage as k., in section 6 of Fig. 16, and thus before 

 it had become joined to the wall of the mother animal, had already 

 formed within itself a new triple generation. A section through such 

 a region therefore passes through no less than nine individuals. 



Of Dictyonema Jlahellifonne, Eichw., I have not had altogether 

 satisfactory material ; a cross-section of this species, however, makes 

 it highly probable that it too is built on the same plan. At all events, 

 its branches are not as simply constructed as those of the Graptoloidea. 

 It was naturally of interest to study how the branching took place. 

 Fig. 17 is meant to show its origin in Dendrogmptus (?) (elandiais. 

 Section a is almost on the same stage as section 6 in Fig. 16. 

 We have thecae i and 2, and to the right the gonangium, which opens 



Fig. 17. — Series of Transverse Sections of Dendrograptus (?) celandicus. 

 For explanation of lettering, see text. 



in theca i in section c. To the left of theca 2 are the three new 

 individuals, of which the larger one in the middle is a theca. Now, 

 if the branch were not about to divide, the upper of the two other new 

 individuals would be a gonangium ; but that is not the case, forMf we 

 go to section b, we see that both the small new individuals were 

 budding individuals, since each has produced three new individuals 

 of ordinary shape. In section c these new ones assume a 

 somewhat different size, and begin to group themselves in two 

 divisions. In section d this grouping has considerably advanced. 

 In c the old theca i is coming to an end, and in / the new branches 

 ^re just about to separate. Of the previously existing individuals 

 that were in the mother branch, in this genus there is in the new 

 branches only one theca, viz., 2. I have noticed almost the same mode 



