248 Kepoet of the State Geologist. 



the colony of Diplograptus from the sicula is certainly homolo- 

 gous to the budding of the Hydroid colony from a sexually pro- 

 duced larva. 



While it thus appears that there is a great similarity between 

 the "gonangia" of Diplograptus and their products, and those 

 capsules of the calyptoblastic Hydrozoa which inclose the sexual 

 glands and their products, there is none at all between "gonangia" 

 and thecae, such as the gemmation individuals observed by 

 Wiman possess. Neither is the possible objection that the gonangia 

 ought to appear on thecae sufficient, for there are living forms 

 enough among the Hydrozoans in which the sexual glands appear 

 on the hydrocaulus. The discovery of siculee only in the gonangia 

 does not exclude the possibility that the latter before that con- 

 tained male or female generative buds which sexually produced 

 eggs, these developing into siculae. Neither the generative buds 

 nor the eggs, which are both always very soft, could be expected 

 to be preserved, while the blastostyle from which these gen- 

 erative glands sprung, and which later gave attachment to the 

 siculaB, is sometimes observed. There is no need of supposing 

 parthenogenesis in the gonangia as the whole difference between 

 the recent and the fossilized gonangia may consist in the non- 

 preservation of the generative buds within the latter, and the 

 longer continued existence of the gonangial test for the purpose 

 of brooding the larv«. 



1 expected that the " pneumatocyst " would be objected to. 

 Yet I thought it my duty to publish the supposition which the . 

 described organ and its peculiarities so strongly suggest. As 

 stated in this report, the pneumatocyst is by no means a heavily 

 chitinized organ ; it can not compare in this regard even with the 

 gonangia. It is true the rhabdosome was inflexible, but this 

 was not in my opinion possible, only because the colony was 

 moored, but it was so in spite of the floating habit of the colony, 

 because it could not be avoided as long as the animals sought 

 protection by a chitin us periderm which was not articulated. 

 There are Sertularidce and CamjpanularidcB to-day which are at- 

 tached to floating objects, and which have a chitinous periderm. 

 The virgula which, according to Wiman, kept the rhabdosome 

 in an upright position, may as well have served to protect the 

 fragile, because inflexible, rhabdosome from breaking ; for if the 



