ON THE DIPLOOHOKDA. 725 



Lastly, there can be little question that we have in the 

 glomerulus a homologue of the proboscis gland of Balano- 

 glossus. Each is a proliferation of the pre-oral coelomic 

 endothelium in the neighbourhood of the pericardial sac and 

 pore canals, consisting of cascal vascular processes. 



It is evident that in the study of the budding processes 

 (10) the origin of the pericardial sac must have been over- 

 looked; but as we do not yet know how this organ arises in 

 the demersal larva of Balanoglossus, nor even with 

 certainty in Tom aria, this is not surprising. From cei-tain 

 indications it appears that in Cephalodiscus it is a portion 

 of the pre-oral cavity constricted off from its posterior end, 

 and therefore coslomic in origin. 



During the progress of my work on Cephalodiscus Cole 

 (1) has published a short paper upon the bulbous termina- 

 tions of the twelve branchial plumes. His results appear to 

 indicate that the migration of oval lens-like bodies out of the 

 epithelial cells to the exterior is to be regarded as a normal 

 process, and that Mcintosh's view (6) that these organs are 

 masses of unicellular glands is correct. Assuming that the 

 migration might be an abnormality, I had suggested that " it 

 seems most reasonable to regard them tentatively as primitive 

 eyes," a view I had already abandoned before the unexpected 

 appearance of . Cole's work. Cole further finds that the 

 glandular bodies break up to form rhabdites, which I think 

 quite probable, especially as I had already found and described 

 indications of '^ one or more areas in the centre (of the bodies) 

 staining more deeply than the rest (7)." I cannot agree with 

 Cole's description of the epithelium in these terminal knobs 

 as normally correct, as such a vacuolated swollen mass with 

 little or no cuticle occurs commonly in other parts of the 

 body, and seems to be an abnormality; the vacuolated con- 

 dition of the bulbs is undoubtedly present, especially in 

 older specimens. Cole denies the existence of a cuticle, of 

 pigment, and of nerve-endings in the cells. In respect to the 

 cuticle I am hardly prepared to inaugurate a discussion upon 

 the line of distinction between a '' peripheral deeply-staining 



