igii.] F. H. Stewart : Development and Anatomy of Cirripedes. 41 



the only form in the later stages is the usual connective tissue nucleus with scanty 

 protoplasm, occurring among the fibres and membranes. 



(4) The yolk is the chief cause of confusion in separating the cellular elements 

 from one another. It is most abundant in the pupa of the male ; somewhat less 

 abundant in that of the hermaphrodite. Some yolk masses are still to be found in the 

 adult male. It is not entirely confined to the peduncle, as it occurs around the stomach 

 and ventral nerve cord in the prosoma. It is of a pale yellow colour and stainS 

 intensely with iron haematoxylin or eosin — not at all with basophil colours or carmine. 

 It occurs chiefly in the connective tissue, which surrounds the vesicular spaces in the 

 peduncle of the pupa. In its most dense form it stains intensely and uniformly with 

 iron haematoxylin (y., pi. v, fig. 4) : after it has been partly absorbed, it has a finely 

 granular appearance (/.g., pi. v, fig. 4). When it completely surrounds a vesicular 

 space, the latter has somewhat the appearance of a yellow cell— hence the "cellules 

 jaunes de la pédoncule" of Gruvel (7a, p. 448). 



The large eosinophil granules which occur in the cement cells of both the male 

 and hermaphrodite pupa and in all but the most completely ripe males are also 

 probably yolk-granules. 



(5) The cement glands and ducts. — The glands are two groups of cells placed one 

 on either side of the midline in the posterior (in the adult — upper) part of the peduncle. 

 In the pupa of both hermaphrodite and male (pi. iv, figs. 4 ' and 6) and in the adult 

 male (pi. v, fig. 3) they are more or less spherical cells with abundant protoplasm and 

 a spherical nucleus. A certain number contain in their protoplasm large granules of 

 irregular shape, whose staining reaction is identical with that of the yolk (pi. v, figs. 3, 

 4). (See Hoek, 8, pi. ii, fig. 5, and p. 28.) The abundance of the granules varies in a 

 manner parallel to the abundance of the yolk (compare Hoek, 8, p. 7) ; they are most 

 numerous in the pupa of the male (pi. v, fig. 4), less in the pupa of the hermaphrodite, 

 onl)^ disappearing in the male when it has reached complete maturity (pi. v, fig. 3), but 

 not found in the adult of the hermaphrodite even at an early stage (pi. v, fig. 5). That 

 is to say, they are gradually, absorbed or extruded with increasing age. They are 

 probably yolk-granules which may or may not be in process of conversion to form 

 cement. In unstained preparations or in preparations stained with carmine the cells 

 containing these granules have a yellow colour (pi. iv, figs. 5 and 6, e.g.) and may be 

 mistaken for the ''cellules jaunes de la pédoncule" referred to above. 



In the young adult of the hermaphrodite (specimens measuring about 2-5 mm. 

 in length, pi. v, fig. 5) the cement cells resemble the non-granular cement cells of the 

 pupa and of the male, but on account of their size it can now be seen that there are 

 certain large granules in the centre of the nucleus which stain more intensely and 

 rapidly with iron haematoxylin than do the ordinary chromatin bodies. In the larger 

 hermaphrodites (16 mm. and upward) the cells (pi. v, fig. 6) are very large (-3 mm.), 

 the protoplasm finely granular. The nucleus (-12 to -2 mm.) is polymorphic and 



^ In pi. iv, fig. 4, the letters e.g. point by mistake to the spaces of the peduncle instead of to the 

 cement glands. The latter structures can be seen as a group of small but sharp nuclei lying above the 

 eye. 



