248 



s. GOTO; 



is wholly unable to attach itself to any object, but helplessly floats 

 about until it has completed its metamorphosis, when it can attach itself 

 very effectively to any substratum, by means of the ambulacral feet 

 which are developed, a fe\v pairs in each radius, by this time. It is 

 also to be remarked that the histolysis of the thickened patches is all 

 but completed in stage G, when the l-arva is still wholly unable to fix 

 itself to any object. 



The degeneration of the thickened patches of the brachiolaria arms 

 brings us to another problem, viz. the function of amoebocytes. I 

 have stated above that these wanderino' cells are crowded in laro;e 

 numbers around the parts that are undergoing histolysis. We must 

 not, however, take this fact in itself as an evidence of the phagocyte 

 action of these cells. It may be a case of simple Chemotaxis, the 

 amoebocytes being positively tactic towards some acid or acids that 

 are ofenerated durins: histolvsis. In fact, so far a« I could observe 

 with the highest magnifying power at my disposal (Zeiss oil imm. 

 Y12) I could not demonstrate the presence of any solid particle in 

 these cells ; it has seemed to me that they assimilate the licpiid 

 substances produced by histolysis. In the transforming stages, i.e., 

 between the almost complete disappearance of the prœoral lobe and 

 the formation of the definitive mouth, innumerable amœbocytes are 

 found in and amon«- the cells of the o'ut. 



O a 



At the end of this section treating of the general form of the 

 body, a few words may be added with regard to the behaviour of the 

 general ectoderm during metamorphosis. It has already been stated 

 that the disappearance of the pra^oral lobe is largely due to a gradual 

 thickening of its ectoderm. The same process of thickening takes 

 place all over the body ; the tentacles are gradually drawn in,, 

 and as these are provided with a thick ectoderm they enter directly 

 into the formation of the oral disc. In doing so, however, they 



