Dr. 0. Serrmann — JDistrihution of Graptolites. 459 



itself appeared to be divided into separate joints by transverse septa. 

 Hopkinson figures a branch of T. serra, Brongn., which was obtained 

 in section and filled with mineral substance. The common canal, 

 which had been occupied by the ccenosarc, has the appearance of a 

 vertebral column, and between each two rectangular joints we see 

 a septum. When the mineral substance was removed, Hopkinson 

 observed a series of rectangular impressions, separated from each 

 other by transverse walls or " ridges." A similar ridge separated 

 each depression from the hydrotheca belonging to it. 



The hydrotheca3, says Hopkinson, appear to have budded from the 

 ccenosarc as the leaves of an exogenous tree bud from the stem, and 

 not to have been continuous with their support like the leaves of 

 endogenous trees. The partition is not a true septum, but only 

 " a ridge, a constriction, occasionally forming a very sharp line of 

 demarcation, but in most cases scarcely, if at all, perceptible." 



The structure here described occurs in the existing Thecaphora, 

 and Hopkinson thinks that " it can now no longer be maintained 

 that the calycles of the Graptolite are not true hydrothecee " : — 

 Kirchenpauer, also, in opposition to Allman, treats the cells of the 

 Graptolites as hydrothecse. 



As regards the Eeproduction and Zoological Position of the 

 Graptolites, no new views have, so far as I know, been recently put 

 forward, so that here we may refer to the excellent section upon the 

 Graptolites in Zittel's " Handbuch der Palaontologie," in which the 

 principal opinions are brought together and discussed briefly and 

 clearly. 



When Hall describes specimens of Diplograptus, M'Coy, with sac- 

 like appendages, and regards these appendages as gonangia, we can 

 only be surprised that among the innumerable specimens of Diplo- 

 graptus from the earliest to the most advanced age which the graptolite 

 collector has the opportunity of studying, such sexual individuals 

 have never turned up. But I have carefully looked for them in vain. 



On the other hand, I brought home a hand-specimen which was 

 sprinkled with small round or oval corpuscles, vividly reminding me 

 in form and structure of the supposed ovarian capsules (Dawsonia) 

 of the Graptolites figures by Nicholson.^ These, like the fragments 

 of Graptolites accompanying them, are converted into grey, shining 

 mineral (Giimbelite ?) But unfortunately the same beds contained 

 not unfrequent although always isolated specimens of a Brachiopod 

 (Obohis !) which has on the surface a striation exactly like that of 

 the small, round bodies. This Brachiopod always aj)pears black and 

 lustreless, and is about six times the size of the latter. Finding at 

 a higher level (zone of Didymograptus MurcTiisoni, Beck, Nordal- 

 Bruns Strasse, Christiania) fragments of slate filled with innumerable 

 small, black, undoubted Brachiopoda {Oholella ?), I became doubtful, 

 and could arrive at no definite answer to the question as to what 

 the grey, shining bodies should be taken for. I must, however, 

 admit that my material was very scanty, and that special investigations 

 can only be made when it is made more complete. 



1 Ann. Mag. Nat. Hist. (1873), ser. 4, vol. xi. p. 140. 



