GRAPTOLITES OF NEW YORK, PART 1 477 



to the Dendroidea, whicli were hitlierto, as regards their internal structure, 

 practically untouched, he demonstrated the complex character of the rhab- 

 dosomes of Dictyonema, Dendrograptus and Inocaulis, proving that they are 

 composed of three kinds of theca. 



The histology of the periderm first received attention from Richter 

 [1871J, and later from Gilmhel [1878]. No very elaborate investigations of 

 the test were made, however, till Perner [1894] undertook the study of the 

 Bohemian graptolites. His results have been modified quite essentially by 

 Wimari's [1895] and GiXricKs [1896] work. [For further details in regard 

 to the histology of the periderm see ch.9, p. 539] 



The mode of reproduction and development of the graptolites is a field still 

 very little exploited. For investigations of this nature, a large collection of 

 growth stages of one species in the best state of preservation is prerequisite, 

 a condition rarely fulfilled. Hall has figured [Can. Grapt. pi. B] some 

 " germs " without referring them, however, to a special type. In his " Notes 

 upon the Genus Grap toll thus " he figured stipes of Diplograptus 

 whitfieldi, bearing saclike appendages, which he regarded as repro- 

 ductive organs. Nicholson [1867] observed numerous variously shaped 

 corneous bodies in the gi-aptolitic shales, which he thought to be remains 

 of capsules, termed " Dawsonia " and held to have been " ovarian vesicles " 

 or '' gonophores " of graptolites. As we shall see presently [p. 738 and 

 under Dawsonia, p. 521], most probably neither of these bodies has 

 anything to do with the multiplication and propagation of the graptolites. In 

 fact, Nicholson'' s assertions were very soon objected to by Carruthers [1868], 

 who insisted that these bodies had no resemblance to the " gonophores " 

 of the Hydrozoa, with which Nicholson had compared them. The same 

 author proposed also to transfer the terminology introduced by Allman 

 and Huxley for the Hydrozoa to the graptolites [for further details see p. 48:^ | 

 and furnished a detailed analysis of the relations of the graptolites to I'ecent 

 similar organisms ; whereby, by a process of exclusion, he concluded that they 

 are most nearly comparable to the Sertularians, but difi:er principally in the 



