KONGL. SV. VET. AKADEMIENS HANDLINGAK. BAND 32. N:0 I. 57 



calicle is nearly ready, the shape of its theca is not circular and the septa are irregular 

 in their size and direction. In vii we have the calicle fully developed and regular. The 

 lacuna on the left side is incidental. 



The description given by von Koch of the coenenchymal gemmation in Heliolites 

 porosus does not agree with iny observations. He says that about twelve tubuli covering 

 a circular surface at once and at the same time arrest their growth and cover themselves 

 with a common tabula and instead of them a calicle appears directly built in the normal 

 manner. I suppose he has been misled by such sections as those represented on his pl. 

 XLiii figs. 7 & 8. Nor can I find how the tigs. 9 — 11 could show the gemmation. If f. 11, 

 according to him, is the oldest and lig. 9 the uppermost or youugest, there is rather the 

 contrary of the gemmation or a destruction of the calicle through change back again into 

 coenenchyma as I am going to describe a few lines below and have delineated on pl. ii 

 fig. 34. It is evident that Nicholson's representation of calicular gemmation in Hel. porosus 

 (page 336 Man. Pateont. 3'' Ed. fig. c au) is nothing else but the same deterioriation of 

 the calicle. The theca is too perfect to belong to a budding calicle on that stage. Compare 

 pl. II fig. 37, sect. v to the left in my memoir. 



We have now contemplated how a new calicle originates, let us no^v turn to see how 

 a mature calicle degenerates and again turns into coenenchyma. from vvhich it was deinved. 

 In sections i and ii there is no change in the regular shape. The change sets in in iii 

 by disorderly growth of some septa at right, as if they were affected by the alterations 

 going on next it, where the first new septa begin to appear. They acquire a new shape 

 or coalesce and so it continues in iv till in v the right moiety is completely destroyed 

 and transformed into a reticular tissue of tubuli which have grown out of the altered 

 septa and it has been converted into coenenchyma. At the left side five or six septa are 

 still visible, but have grown longer and coalesced with each other and formed tubuli. 

 In VI the whole has tui'ned into coenenchyma of an irregular appearance, and at the surface, 

 of the corallum, vii, it is changed into a regular coenenchyma where all vestiges of the 

 lower buried calicle are effaced. 



Both these parallel, collateral series of sections were taken at a distance of 0,i mm. 

 from each other. The distance between sections vi and vii is 0,6 millim. 



In figs. 3 — 4 pl. III another instance is given of this selfdestruction of the calicles. 

 In fig. 3 the calicle has proceeded far in the coenenchymal metamorphosis, the tig. 4 

 showing the appearance of the same calicle a little below the former. This change is 

 in contradistinction to another of the same effect, when the coenenchyma incroaches upon 

 the calicular area and destroys it by overwhelming it. 



Metamorphic agencies have been at work in the interiör of the polyparia. Ås it is 

 possible by degrees to foUow the alterations, no mistake can be made to attribute to organic 

 structure what is in fact inorganic destruction. Thus in a transparent section at one side whei'e 

 the structure is intact the calicles have their twelve septa. In an intermediate patch between 

 this and the metamorphosed region the calicles have partly löst some septa and the rest is 

 rautilated, while on the metamorphosed side they are like the calicles of Hel. decipiens. 

 The regular outlines of the calicles and the normal form of the septa left in situ on the one 

 side prove, however, sufficiently that this change is caused by other than organic changes. 



