380 On the Morphology/ and Affinities of GraptoUtes. 



graptolite. From his account of their relation to these, how- 

 ever, I can recognize nothing but accidental proximity ; while 

 if we admit that he has grounds for this belief, we should then 

 have, in the advancement of the embryo to a stage in which it 

 has become covered by a chitinous perisarc previously to libera- 

 tion, a state of things quite at variance with all we know of 

 the reproductive phenomena of living hydroids. 



It is not improbable, however, that these graptolite " germs" 

 of Hall are free zooids rather than true embryos, and that they 

 had been originally thrown off by a process of non-sexual re- 

 production from some part of the living graptolite in a manner 

 which reminds us of somewhat analogous bodies which I have 

 elsewhere described as becoming detached from true hydroids 

 in the case of Schizocladium and of Corymorpha. As we de- 

 scend through the great biological groups it is no uncommon 

 thing to find the faculty of agamic reproduction becoming in- 

 tensified, until in the lowest members of the group we see it 

 (as in the case of the gulf-weed already referred to) taking more 

 or less the place of true sexual generation. 



But little requires to be said regarding other views which 

 have been from time to time advanced as to the affinities of 

 graptolites. 



Their alleged polyzoal affinities, however, have some claim 

 on our acceptance. Indeed, were it not for the discovery 

 of the probable graptolite gonosome (corbulse?), we should 

 have nearly as much to say for this view as for that which 

 would refer them to the Hydroida, more especially as the dis- 

 covery oi Rhabdopleura renders us acquainted with a polyzoon 

 in whose test is developed a chitinous rod in almost all respects 

 like that of the graptolites*. 



On the whole, then, it would seem that the graptolites con- 

 stitute a very aberrant hydrozoal group having manifest 

 affinity with the Hydroida, to which they are connected by 

 the nematophore-bearing genera of the latter, while they have 

 also important points of connexion with the Rhizopoda. The 

 undoubted members of this group are further characterized in 

 an eminent way by the possession of a solid supporting rod ; 

 and it is this feature which has suggested to me the name of 

 Ehabdophoea, by which I have proposed to designate them. 



* The comparison of the rod of Rhabdopleura with that of a gi'aptolite 

 has ah-eady been made by Dr. Nicholson (' Manual of Zoology '), though he 

 adopts the more generally accepted view which finds hydrozoal rather 

 than polyzoal affinities in the graptolites. 



