cxxiv BRITISH GRAPTOLITES. 



Dendroidea, drawn up as they wore when practically nothing was known of their 

 structure, are now of little value, bnt he admits that a new classification would 

 as yet be impracticable and inadvisable. 



As respects the systematic position of the Graptolites he considers that it is 

 impossible to say more than that the " Graptolites are bilaterally symmetrical 

 invertebrates." 



Phylogeny. — Wiman discusses the relationship between the Graptoloidea and 

 the Dendroidea, and considers that " they are two parallel stocks of equal value 

 in which the division of labour is performed in somewhat different ways." 

 " In the Graptoloidea the different functions (while all the individuals of the 

 first order remain the same) are shared among different organs." " In the 

 Dendroidea, on the other hand, the different functions are shared by three different 

 forms of individuals of the first order." 



The theory that the Graptoloidea are descended from the Dendroidea seems to 

 him very improbable ; while the reverse idea, namely that the Dendroidea are 

 descended from the Graptoloidea, meets with greater favour, as it is usual for 

 " division of labour in a colony to bring about a difference of individuals." 



The mode of life of the Graptolites is next dealt with, and Wiman concludes 

 that the only possible view to take is that " the Graptolites, in some way or other, 

 stood upright " and lived in the " deeper littoral regions." 



The paper concludes with an Appendix giving an abstract of Ruedemann's 



discoveries of colonies of Dvplograptus attached by their virgulas, and some of the 



points referred to there are discussed and criticised. Exception in particular is 



taken to Ruedemann's idea that these colonies were provided with a swimming 



bladder. 



Considerable light had already been thrown on the mode 



of life and development of the Diplograptidse by Ruedemann's 



„ r, • „ ,, ,„• -, discovery of some remarkable specimens ot forms referred by 

 " Synopsis ot the Mode J i j 



of Growth and Develop- nmi t° Diplograptus pristis and Dvplog. pristiniformis (af fer- 

 ment of the Graptolitic wards named Ruedemanni). The first notice of this was 

 genus Diplogruptus," given in an abstract published by him in the American 

 •Amer. Journ. cf Sci.,' Journal of Science. 



ser. 3, vol xlix, no. 294. ... . 



Ruedeinann summarises Ins conclusions as follows : 



(1) These two species grow in " compound colonial stocks which appear in the 

 fossil state as stellate groups." 



(2) "The virgulse are joined to a central connecting stem, the 'funicle' of 

 Hall, which is mostly extended to a vesicle of quadrangular shape." The funicle 

 is " enclosed in a central disc " which is a " thick, chitinous capsule " also 

 quadrangular in shape. 



(3) " The central disc is surrounded by a verticil of oval capsules," in number 

 four to eight or more. Some of these oval appendages are seen to contain siculse 



