2. Larval Stages and Fixation. 



41 



section fig. 16) is taken through the extreme anterior end of the head and on the right side 

 is seen one of the Frontal glands. These glands are of a true cellular nature, and not as 

 Delage supposed non-cellular accretions. 



The Nauplius with the structure described is now soon ready to be hatched out of 

 the mantle- cavity. 



2. Larval Stages and Fixation. 



The free swimming Nauplius of Sacculina cartini has been minutely described by 

 Delage (2) and since the Nauplii of Sacculina neglecta and S. benedeni agree with his description 

 and figures in every detail, I will only refer the reader to Plate 4 fig. 17, which depicts the 

 Nauplius of Sacculina neglecta from the ventral view. Delage points out that the newly-hatched 

 Nauplii appear under two forms, a round and a long form; but this is only due to the long- 

 forms having already accomplished a moult on hatching. This is also true of Sacculina neglecta, 

 our figure being taken from a long-shaped larva. 



Plate 4 fig. IS depicts the Nauplius larva of Peltoe/aster curvatus. 



The transformation of the Nauplius into the Cypris has been described with the minutest 

 detail by Delage, and he also gives instructions for rearing the larvae. 



His account of the larval stages and of the fixation are the most elaborate and careful 

 parts of his memoir, and since my own observations on this subject have been far from 

 successful (see Note p. 44), I cannot do better than follow his account, only adding confir- 

 matory remarks of my own where I am able to do so. 



The Nauplius of Sacculina undergoes four moults in five days in order to achieve the 

 Cypris stage. These moults do not effect any change in structure until the last moult which 

 discloses the fully formed Cypris. 



The Cypris larva of Sacculina ne</lecta is figured in our Plate 4 fig. 19; it resembles 

 in all points the Cypris of Sacculina carcini. The cephalothorax bears a pair .of antennae 

 furnished with hooks, and also a pair of H-shaped "chitinous tendons" which are very con- 

 spicuous. There is a conspicuous pigmented eye, and a pair of glands on each side, the four 

 openings of which are shown in the figure. Posteriorly the large cells in the thorax of the 

 Nauplius have given rise to six pairs of biramous thoracic limbs; the abdomen is exceedingly 

 small and rudimentary. Beside these organs there is a mass of cells, which Delage calls the 

 ovary, but which for reasons that will be given, I prefer to call the "embryonic cells"', situated 

 as paired lateral masses on either side of the cephalothorax [Em Plate 4 fig. 19). These 

 embryonic cells of a lately fixed Cypris, found upon the dorsal surface of the carapace of 

 Inachus scorpio, are shown in horizontal section in fig. 20. They are derived from the mass 

 of mesodermal cells situated in a similar position in the Nauplius larvae [Em Plate 4 figs. 17 



Zool. Station zu Xeapel, Fauna und Flora Golf von Neapel. Khizocepbala. g 



