Mr. H. J. Carter on the Poljtreniata. 203 



of what is seen in Halisarca guttula, and if arrested in this 

 stage of development would be almost identical ; but when 

 the cell-mass of the embryo is ' told off ' into the organs 

 which the J are to assume in the fullj developed Ascidian, 

 then of course the difference at once becomes obvious." 



This view has been opposed with no small amount of acri- 

 mony by Prof. A. Giard, of Lille, who published his " Re- 

 cherches sur les Synascidies " (Compound Tunicata) in the 

 first volume of Lacaze-Duthiers's 'Archives de Zool, exp^ri- 

 mentale et g^n^rale,' and in the second volume (viz. that for 

 1873, p. 481) dwells on what he considers to be the resemblance 

 between the " Myxospongiaires et des Synascidies," viz. " mi- 

 mdtisme," whence he suggests for a supposed new species of 

 Halisarca the name of H. mimosa. Now, it being a matter of 

 opinion whether my likening the embryo of some of the Com- 

 pound Tunicata to that of the Halisarcida, as above mentioned, 

 is in favour of the " theory of evolution" or that of " mimicry," 

 the question is not worth disputing ; " le jeit ne vaut pas la 

 chandelle.^'' But when Prof. Giard comes to translate my 

 words above mentioned, viz. '' almost identical " into " II 

 y a identity complete" [op. et torn. cit. p. 490), it is very evi- 

 dent that it is not a matter of opinion whether he has or has 

 not falsified my assertion ; it may, however, be still a matter 

 of opinion whether Prof. Giard can or cannot read English ; 

 and so far it would be only charitable to assume the former. 

 But still the fact remains to cast a doubt unfortunately 

 over the rest of his statements — a doubt which, considering 

 their apparent value, I would most willingly have not enter- 

 tained. 



lieturning now to Polytrema halaniforme^ we observe that 

 the most striking feature, next to its form, is the coarseness 

 of its structure, not only when compared with that of Poly- 

 trema miniaceum^ but with that of all the other large Forami- 

 nifera known, together with the comparatively enormous size 

 of its internal cavities and the quantity of spongc-s])icules, 

 both entire and fragmentary, agglutinated together in 

 massive accumulation, that they contain. Having had to 

 truncate one of my specimens for structural examination, 

 several fragments of the sponge-spicule accumulations fell 

 out, which, on being decalcified by the aid of dilute nitric 

 acid and mounted, gave almost innumerable forms, one of 

 which (viz. a bihamate, with a serrated crest of recurved spines 

 extending some way backwards on the outer side of each 

 extremity?) is quite new to me (fig. 10). It gave me also the 

 opportunity of examining the calcareous portions under a 

 higher power (viz. ^-inch object-glass), which were thus foun(l 



14* 



