172 Proceedings of the Royal Irish Academy. 



suggests a sexual association as a possible explanation of the condition in 

 question. He lays stress upon the fact which we have ourselves observed in 

 the tests now under discussion, viz. : that the first chamber of the spiral series 

 is placed as it were astride of the flattened or plane septum dividing the 

 twin primordial chambers, which he regards as proof that this latter chamber 

 is formed by the equal fusion of the protoplasmic contents of "the two 

 primordial chambei^. 



The diameter of the megalosphere, measured across the interior of the 

 chitinous wall so as to eliminate tlie varying thickness of the sandy wall, 

 averages 70/i, but primordials have been measured as low as 50/<, and as 

 high as 90/i, though ihese exceptions are rare. A primordial exhibiting an 

 internal septum was found to be 50 x 6S/i. 



The mierospheric form (b), on the other hami, is short, and has a sharply 

 pointed test, commencing with a number of minute chitinous chambers 

 invested with very fine sand (fig. 9). The arrangement of these chamber's is 

 not always easily identifiable. They are sometimes acervuline, sometimes 

 in a flatt«ned, rotaline spire, sonietimcs apjiarently spimjileetine. Or it may 

 perhaps Ije always a spiroplectine armngement, set at uitl'ering angles to the 

 main axis, and so presenting different aspects. These early chambers are 

 followed by numerous triserial chambers, very small at first, and then 

 rapidly increasing in size so as to give a turgid appearance to the test. The 

 chambers are chitinous under a sandy investment for some distance from the 

 apex, and they are very numerous as compared with the megalospheric form 

 (fig. 10). The microsphere is not always easy to discover or measure, as it is 

 often surrounded by a mass of small chaml>eis, spirally or irregularly arranged ; 

 but a careful series of measurements gives an average of i:5-1.5/i. A few 

 individuals were found with larger microspheres, including one of 2bfi and 

 one of 30m. 



All the (6i short broad forms appear to be invariably mierospheric. A 

 few of the long forms are to be found which, instead of lieing blunt and 

 rounded at the apex, are finely pointed, and these are mierospheric also. 



We had in past years observed an occasional dwarf specimen of 

 VirntuUina ]>oii/siro]iha in seveial Goldseeker dredgings, but without 

 realizing that they possessed any particular interest. But in 1913, when we 

 found these dwarfs in material which we were examining for our Clare 

 Lsland paper, we realized that they were exact facsimiles of the normal 

 type in constructi'^n, number of chainbers, and the existence of a long form 

 and a short fonn." The only points of difference appeared to be the relative 



♦* Loc. cU. (nute 7), fig*. 3-5. 



