232 



should not feel justified in giving him a tu quoque, and accusing 

 him of erroneous assertions and exaggerations. 



The same remarks apply in general to nearly all the structural 

 features of the larva. The nerve-ganglion, the lower mesenteries, the 

 two pleurochords, had all been noticed to a greater or less extent by 

 observers of such a standing as Metschnikoff, Kowalevsky, and 

 the others named. Whilst my work falls in to line with such authori- 

 ties, it is a matter of minor importance that it does not agree with that 

 of Professor Roule. 



The criticism, that I ought to have followed the early stages, has 

 also been made by others equally ignorant of the facts. The adult 

 Phoronis does not occur in St. Andrews Bay, and I question if it would 

 have been justifiable to Avithhold my paper for some years till an oppor- 

 tunity presented itself of following the young stages. Further, if the 

 mesenchymatous origin of the mesoderm were proved I cannot see that 

 it would make the least difference to the conclusions drawn from the 

 structure of Actinotrocha, any more than the different origin of meso- 

 derm in Amphioxus and Tunicata keeps these apart. In other words, 

 the conclusion drawn from the structural identity of Actinotrocha and 

 the Hemichorda could not be allowed to depend solely upon the origin 

 of the mesoderm. 



3) Phylogenetic conclusions. 



But though Professor Roule's observations are sufficiently start- 

 ling, they are far excelled by his inferences. Briefly, he places Pho- 

 rotiis beside Cephalodiscus ^ whilst flatly denying the existence of all 

 the fundamental resemblances which caused me to make a similar 

 approximation. Further, he denies that there is any real resemblance 

 between Phoronis and Balanoglossus^ apparently unaware that it was 

 the structural resemblance between these two, as described (Proc. 

 Royal Society Edinb. March 1895), that led me to suggest its alliance 

 with the HemicJiorda^ and to search for a chordeid structure in the 

 larva. But this is not the end. The mouth oî Phoronis = a blastopore", 

 the anus of Balanoglossus = a blastopore ; therefore the mouth of 

 Phoronis = the anus of Balanoglossus ! 



As the Professor says truly — "La concordance est complète. 

 L'homologie est manifeste!" 



Further, Phoronis is to be compared to Balanoglossus turned up- 

 side down. As Phoronis is comparable, part for part, with Pterobran- 

 chia^ to get the true relationship between Gephalodiscus and Balano- 

 glossus we must turn one round and over. The proboscis of Balano- 

 glossus has to be sought for in the trunk of Cephalodiscus, the 



