Prototlteca of the Madreporaria. 13 



remarkable genus. We have the same three elements, proto- 

 thecal tubes, tabula 1 , and spiny septa*. 



(e) The habit of tailing over is known still to occur in the 

 genus Flabettum. 



(/) Lastly, I appeal to the modifications of the prototheca 

 which will be described in the following pages, every one of 

 which may be regarded as an adaptation for the purpose of 

 solving the problem of vertical stability, that is, how to avoid 

 the natural consequence of having to stand on a point while 

 continuing to grow in height and bulk. For we are surely 

 justified in assuming that the falling over at the very outset 

 of life of an organism intended, if we may say so, to stand 

 upright, would mean considerable loss of time and energy 

 during the reattainment of the upright position. Such a loss 

 might be expected to delay budding, and it is probable that 

 we may have to take this into account in our ultimate classi- 

 fication. We may have to form a group which arose from the 

 early budding of parents still in their prototheca} (sens, sir.), 

 and this would include such forms as Aulopora, SyringopoTa s 

 and Halysites, in all of which the prototheca^ fell over, and to 

 these we might add Chcetetes arising probably by fission. 

 Whether the prototheca also fell over in this last case I have 

 not ascertained. Such a group arising from parents still in 

 their protothecre proper, would stand in contrast to another 

 group in which the budding was delayed until the polyp had 

 grown considerably larger and had again assumed the upright 

 position, and our divisions of these latter would have, in the 

 first instance, to be based upon the methods adopted to attain 

 this end. 



II. Radicle-formation.— -This process has been carefully 

 studied and described in Flabellum by Lacaze-Duthiers f. A 

 small portion of the lip of a prototheca bends over until it 

 adheres to the ground (si:e diagram fig. Sa,b). I have myself 

 seen a similar process as an occasional thing in young colonies 

 of Alveopora. It is difficult to see how the great pear-shaped 

 colonies in this latter genus could possibly stand upon the tip 

 of the original prototheca without gaining support on this 

 principle. Extensive droopings of the rim till it touched the 

 ground with subsequent bends up again are probably more 

 common in this genus than the formation of thin radicles. 



Root-processes may come from the rims of different proto- 

 thecai in those cases in which the corallum is built up of a 



* Cf. Fischer-Benzon, Abhandl. wissench. Ver. Hamburg, Bd. v. 2 



(1871), pp. 1-^3. , . 



t Arch. Zool. expe"r. (3) ii. 1894, p. 44o, pi. xvni. 



