Correspondence — Dr. Nicholson. 151 



In answer I have simply to state, that my paper was intended to be 

 simply an abstract, and " summary " of a more detailed one, which I 

 trust may one day see the light, and that it was, therefore, impossible 

 for me to enter into minutiae. Secondly, though perfectly aware of 

 this existence of free and corneous Polyzoa (the Ctenostomata of 

 Busk), the above statement nevertheless remains true of the 

 Polyzoa, '^ as a rule,"" and I see no reason for altering it. 



2. Mr. Carruthers charges me with adopting a statement of Hall's, 

 as to the free mode of existence of Graptolites, without acknow- 

 legement. To this it is quite enough to reply, that the statement in 

 question was not made as an original observation on my part, and 

 that it is impossible in a general paper to quote references for all 

 the facts which have been previously noticed. As to my making a 

 " practice " of so doing, no denial on my part can be needed. My 

 published papers on the subject bear ample witness how much I am 

 indebted for real solid information to the writings of Hall, Salter, 

 Harkness, Barrande, and Geinitz. The changes in my views, to 

 which Mr. Carruthers refers, have been the result of the progress of 

 my own researches, and I could not, with honesty, attribute them to 

 any " corrections " from Mr. Carruthers. 



3. As for my use of the word "gonophore," instead of '^gono- 

 theca," to signify the external bell-shaped ovarian capsule of the 

 SertularidaB, it will suffice to make the following quotation from 

 Prof. Greene, whom, I suppose, Mr. Carruthers will allow to be some- 

 what of an authority upon the Hydrozoa. ''In the Sertularidse .... 

 the reproductive bodies appear externally as distinct buds or sacs, 

 for which Prof. Allman has proposed the name of ' gonophores ' " 

 (see Coelenterata, p. 40) . This is but one of many similar statements 

 in the same work, but it will, I imagine, be sufficient to justify my 

 employment of the term. 



4. With relation to the genus Pleurograpsus, the facts of the case 

 are simply these. In 1852 Geinitz proposed the name Cladograpsus 

 to include certain Graptolites (species Gemell^, Bronn.), comprising 

 Diplograpsus ramosus, Hall, and several species of Didymograpsus. 

 In 1859, seven years afterwards, Mr. Carruthers applied the same 

 name to a very peculiar branching Graptolite from Dumfriesshire, 

 without giving any generic characters of any kind, an omission which 

 he failed subsequently to rectify. The same Graptolite was described 

 by me in March, 1867, in a paper read before the Geological Society of 

 Edinburgh, in which I described it as the type of a new genus, 

 giving a full diagnosis, and terming it Pleurograpsus. (See also 

 Geol. Mag. Vol. IV. No. 6, June, 1867.) In June of the same year, 

 Mr. Carruthers re-described the species as a Cladograpsus, this time 

 assigning characters to it as a new genus. As, however, these 

 characters are totally different from those of the original genus of 

 Geinitz, and as I was the first to give any generic description, the 

 name Pleurograpsus must obviously be retained. 



Finally, to the personalities with which Mr. Carruthers has seen 

 fit to adorn his paper I shall return no reply, considering them 

 unworthy of any genuine scientific controversy. I shall content 



