682 A NEW ENDOPAKASlTlC COPEPOD, 



Two eye-spots are present over the brain. Eacli oi' these is a 

 granular elongated cell, one end coming to the dorsal surface and 

 pigmented, the other, in contact with the brain. On either side of 

 the brain dorsal thereto, there is a medium-sized cell, with coarsely 

 granular contents, and taking borax-carmine stain deeply. These 

 are evidently glandular, perhaps larval kidneys. 



The darkly staining belt is doubtless a paired mesoderm-band. 

 The two cells dorsal to them are also mesodermal, and in the 

 nauplius occupy practically the same position, and have altered 

 only in that they take the stain more deeply. They are probably 

 the primordial germ-cells. Their stability through a period of com- 

 plex changes in all other regions, was what first suggested this to 

 me, and it has since occurred to me that they are situated one on 

 each side of the archenteron, at what must ultimately become the 

 anterior end, and slightly dorsal to the midline. 



The large cells which have aggregated to themselves the fat of 

 the degenerated mass, are doubtless the endoderm cells, and consti- 

 tute a potential archenteron. 



The origm of the brain and of the larval kidneys, is quite un- 

 known to me from actual observation ; though one luight discuss 

 their probable origin from analogy. It is, however, worthy of note 

 that the cells of the larval kidneys ai-e essentially similar to the 

 adult subdermal glands described on page (375. 



Though 1 have the stages of development fairly complete, (see 

 Figs. 41-44), and although I have examined those specimens care- 

 fully, I am quite unable to describe a single phase in tlie formation 

 of the muscles. The suddenness of their appearance is truly sur- 

 prising; in one stage, no trace of muscle is visible; in what would 

 otherwise appear to be a stage closely following, the whole of the 

 muscles are present. 



I have now described, as far as my material permits, the internal 

 organisation of the Nauplius; it remains to describe, as far as is 

 possible, the history of the external form and the appendages. 



The embryo, until the appearance of the ectodermal cap, pre- 

 sents only an anterior pole (thinner), and a posterior pole (thick- 

 er), dorsal and ventral sides being indistinguishable. Very soon 



