56 G. LINDSTRÖM, HELIOLITID^. 



I regard it as liomologous, as well as with Miss Ogilvie's centres of gvowth. I have not 

 been able to detect any structure in this central stratum, it seems to be homogenous. 

 The two lateval strata consist entirely of ininute tibrilke, which in a longitudinal 

 section are directed upwavds from their basis, be it on the exteriör or tlie intei'ior side 

 of the theca. The septal lamelliv consist of sucb, as well as the coenenchymal tubuli. 

 But there is no double wall to the calicle for itself, it shares the outer moiety with the 

 adjacent tubuli, which also share their walls with the adjacent ones. The median stripe 

 is common to them all, radiating without interruption between all calicles and all tubuli, 

 it is, as it were the primary sceleton of the polyparium. Only the septa, Avhich present 

 themselves as direct offshoots from the interiör stratum of the theca and entirely dependant 

 of this, consist of two strata, indistinctly divided by a white stripe which apparently 

 comraunicates Avith the central stripe. To judge by this, joint with the observations of 

 the small initial polypierite, the usual rule, that it is the septa which form the wall by 

 uniting their exteriör parts, does not hold good here and it is on the contrary the wall 

 01" theca, which is the primary part from which the septa grow out as well as the coenen- 

 chyma. The distinct strawcolour or påle yellow which characterizes all the vertical con- 

 stituents of the polyp sceleton in Heliolites viz., thecje, septa, septal spines and walls of 

 the coenenchvmal tubuli, testities to the common origin of all. 



Genimniion. The only one which I have been able to observe in this species is 

 the coenenchymal. The seven sections pl. ii fig. 37, i — vii, repi"esent the successive changes 

 of two calicles, by a happy coincidence actually fonnd beside each other. This series of 

 sections was obtained by cautiously rubbing down from the surface a portion of an Eiflian 

 specimen having the aspect as presented in fig. 37, sect. vii. The entire length thus abraded 

 from VII to I amounts to 1,2 millim. In the deepest section i, to begin from the beginning, 

 we tind to the left a perfect, fully developed calicle and at right the common coenenchyma, 

 of which, however, two or three tubuli seem affected, having a deeper tinge. As the 

 changes in these two series of calicles are diametrically opposite we leave the left one, to 

 continue with the budding one. In section ii seven tubuli are affected, of them the two 

 lowest, the same as in i, have grown larger; six are grouped round a central one. They 

 grow still more in size, sect. iii, and the central one as well as the two tubuli right of it are 

 much changed, the walls between them partially broken and vanished, reduced in size, 

 dwindling to threadlike thinness from at tirst being thick. The lirst indication of septa is 

 \isible on the right side in a bifurcation which in the next stages has grown out into two septa. 

 A step further in sect. iv, all walls towards the centre, where it is an open space, have been 

 absorbed, there is free intercommunication between all seven tubuli now changed into open 

 compartments between their lateral theca^, changed into narrow, irregular septa eight or nine, 

 and the whole is surrounded by an incrassated börder, the hrst irregular indication of the 

 future theca, partly formed of the remaining fragments of tubular thecse, but, however, not 

 regularly circular. Two more tubuli. one in the uppermost left corner, one in the lowest, 

 have been attracted within this spha?re of change and out of these have, sect. v, been 

 formed two new loculi and the number of septa is complete, though thev are of much 

 uneijual size owing to their successive appearance. Some are formed out of old tubuli 

 walls, others, the smallest, are formed auew and grown out of the theca. In vi the new 



