KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 49. N:0 4. 7 



other, thus giving rise to a network with finer and wider meshes. The absorbent 

 syncytia are incessantly changing, their appearance at one moment being quite differ- 

 ent from that at another. Presently the pseudopodia begin to withdraw again, 

 causing a gradual disappearance of the meshwork, and simultaneously other protru- 

 sions are sent out, constituting new meshes and new Communications with neigh- 

 bouring cells. 



But while these changes are going on, the main granular portion of the cells 

 which constitute the absorbent syncytia is by no means immovable. When a coarser 

 pseudopodium has been protruded, it often extends itself further, forcing the gra- 

 nular portion with its nucleus to change place and to pass gradually into the clear 

 pseudopodial protrusion. 



This mode of operation is something quite different from that of the t nio 

 amoeboid cells of the blastocoel, which do not form more than simple and tempo- 

 rary meshworks. 



Let us now return for a moment to the calciferous syncytia, in order to con- 

 sider their mode of operation. 



It is a Avell-known fact that the first stage of the pluteus is characterized by 

 possessing only two centres of calcification, which during the growth of the larva 

 give rise to the two spicules or rods, which support the posterior ventral arms. 

 These two rods — I pass över all the other subsequent rods of the more advanced 

 pluteus, because they originate in the same way - - and their branches are bilateral 

 in position and symmetrical in shape, and present quite the same appearance; only 

 very inconsiderable differences being noticeable with regard to the small unimportant 

 lateral spines. How to explain the remarkable fact, that two bilateral calcareous rods 

 of exactly the same shape originate simultaneously within the hollow lar val cavity, 

 and are able to increase there, in order to assume a definite and characteristic aspect. 

 As far as I know, nobody has made an attempt to explain this mystery. Por my 

 own part, I think there is only one acceptable explanation of this problem. 



My opinion is as follows. The two earliest centre of calcification consist of two 

 small syncytia of close-lying, fused amoeboid cells, which remain bilateral and sepa- 

 rata In each heap of cells the clear peripheral plasm has flowed together and mixed 

 so as to form a syncytium. Within each of these syncytia an extremely small calca- 

 reous corpuscle arises, which rapidly grows and finally takes the shape of a charac- 

 teristic rod, one on each side of the pluteus in its first stage of development. This 

 has happened owing to the two syncytia in question having prepared the way for 

 the future rods, and the process seems to be governed by a general law. For the 

 marvellous and rapid increase of a microscopical calcareous particle into a compara- 

 tively large rod, which in all normal larva? has an almost absolutely definite and 

 fixed shape, and which, besides, has arisen in a hollow body-cavity, cannot be ex- 

 plained in any other way. The two symmetrically arranged rods must be entirely 

 due to the activity of the two syncytia and their pseudopodia, besides which there 

 must be laws which regulate their operations. The two first formed centres of calci- 



