202 TWENTIETH REPORT ON THE STATE CABINET. 



as the common body in its canal along the axis, gives origin to the budding 

 which developes the successive cellules and the gradual building up of the 

 polypary. 



The earliest condition of development is illustrated in fig. 12 of Plate 

 i.* At a farther stage of development we have the form better defined, 

 as in fig. 13, where the germ has assumed the general aspect of G. pristis, 

 the slender lateral processes being rectangular to the axis. 



On the left hand of fig. 8, and at the third reproductive sac below the 

 top, there are two germs visible, close to the. sac, where the connection 

 between one of these and the fibre is nearly complete. The same is shown 

 in the enlarged fig. 11. 



In figure 14 we have the germ of another form, which is unequally 

 developed on the two sides. Figure 15 (represented of the natural size) 

 appears to be of the same species, having reached a more definite form. 

 Figure 16 is an oval disc, of which several more or less defined specimens 

 have been found among the young graptolites, but I have not been able to 

 trace it to any known mature form. 



The specimens figs. 17 and 18 appear to be the young of G. bicornis, or of 

 a similar form. In one the body is narrow, without marks of cellules, and 

 the solid axis is not extended above the common body, having probably been 

 broken off". In the other there is a greater expansion of the common body, 

 but no cellules are visible, and the central portion of the substance is more 

 dense, while towards the margin it is extremely thin ; the solid axis is 

 extended beyond the stipe, and the lateral oblique processes are quite 

 perfect. This germ, with its axis and common body, had not begun to 

 develop the cell-apertures on its margins, which may be seen at a later 

 period. 



In nearly all the young graptolites, there is an extension of the common 

 body along the axis above the incipient cellules. This is observed in the 

 figures referred to and in the young of G. ramosus, shown six times 

 enlarged on Plate ii, fig. 21. . ' ' . 



Although I have found none of the monoprionidian forms with repro- 

 ductive sacs attached, I have nevertheless observed what appear to be the 

 young of some of these species, having an aspect similar to the others, 

 except in carrying the development upon one side only of the solid axis. 

 An illustration of one of these forms is given in fig. 19, Plate i, showing 

 the base irregularly divided. These forms cannot be referred to any known 

 mature species. 



This mode of development, illustrated in numerous specimens, can be 

 readily understood in the simple stipes, whether of the monoprionidian or 

 diprionidian character. Admitting that the examples given furnish 

 evidence of the mode of reproduction of the diprionidian forms, or those of 

 the Sub-genus Diplograptus, where we have a range of cellules on each 



* All the specimens of germs or young graptolites are six times enlarged, except figs. 

 11 and 17. 



