1 64 Proceedings of the Royal Irish Academy. 



with ehitiii, or have added a chitinous ehamberlet to their otherwise normal 

 shells. Amoug the monstrosities found in our Selsey Tanks was a perfectly 

 twinned specimen of MassUina secans (d'Orb.), which had added at the 

 junction of the shells, to serve as a general aperture, a wild-growing tube, 

 and the whole of this monster was purely chitinous (fig. 5). 



In 1884 von Daday recorded a form, a chitinous polythalamian Ehizopod 

 from the salt-pools of iJeva in Transylvania, for which he established a new 

 genus and species Entzia teirastomcUa'", which appears to be closely related 

 to if not identical witli the accepted genus Trochammina — a genus which, as 

 we have recorded elsewliere, is peculiarly apt to form its test for the most 

 part of chitin, supported by very few and separated quartz grains." This 

 chitinous depauj>erati<>n in our specimens has usually been due to a deficient 

 salinity, whereas in von Daday's organism the same variation appears to 

 arise from a contrary condition of things — viz., excessive salinity. The most 

 interesting feature in von Daday's discovery, and one which is very germane 

 to the question.^ at issue in this paper, is the origination and evolution dc novo 

 in inland watere of a polythalamian form, hitherto invariably connected with 

 a marine habitat. 



We desire to speak wiili great i-eserve and caution upon this subject, in 

 view of the very limited amount of information as yet obtainable I'especting 

 the nature and origin of chitin. We have yet to learn how it is secreted by 

 the foraminifer, and how it may be definitely identified, but we may put 

 upon record the facts recorded above, and also that such cliitinous specimens 

 have been found under all conditions of normality, starvation, and satiety, 

 at all temperatures, and at widely dilferent depths. Wliat is required is 

 data upon which to form an opinion whether the secretion of chitin in 

 abnormal quantity is (a) merely a diversion of the normal function of the 

 protoplasm — viz., the secretion of a shell either by the use of adventitious 

 material, or by the separation of carljonate of lime from the sea-water, in 

 which case this form of variation may prove to be the key to the problem of 

 isomorphism : or (6) whether chitinous variation lias a distinct biological or 

 pathological meaning. 



(vi) It may become a question — but it is one upon which we are not at the 

 present moment prepared to enter — whether to the five modifications which 

 we have now considered a sixth should not be added. This is the question 

 of free and adherent forms of the same species. Many forms are found at 



*^ E. v.in Daday: "'Ueber eine Polythnlamie tier Kochsaltztvimpel bei Deva in 

 Siebenhurgen, " Zeiuchr. f. Wiss. Zool., vol. xl, 1684. p. 46.5 «/ «7. (Transl. Ann. Mag. 

 X«t. Hi«., Ser. 5, vol. xiv, 18&4, p. 349. ei atq.) 



" L->c. cit. (note 7), p. S2. 



