28 THE VOYAGE OF II. .M.S. CHALLENGER. 



indeed be regarded as .such. Krohn has not given a description of these glands, nor is 

 such a description fco be found in the literature of the group. For Balanus I myself 

 published figures of these glands some years ago, 1 when it was my opinion thai the 

 ovarian cceca might perhaps develop from these bodies — a serious error pointed out by 

 Claus. My excuse was firstly that these bodies, scattered everywhere between the 

 young ovarian cceca, had never been observed in a .sessile Cirriped before, and secondly 

 that Darwin had led me into error by describing the cement-glands as adhering to the 

 basal membrane or basal calcareous plate of the Balaninse. I should have paid mure 

 attention to a footnote in Krohn's paper (p. 357), in which he states his opinion that 

 the true cement-glands of the Balanidse might also be found between the ovaries or in the 

 connective tissue surrounding the mantle. 



The cement-glands of Lepas anatifera, of Conchoderma virgatum, and of Scalpellum 

 vulgare arc nearly of the same shape and size. Those of Lepas anatift ra are a little larger, 

 the longest diameter measuring 0'15 to 0"2 mm., whereas those of Scalpellum nilijare are 

 smaller, having a diameter of about 0"125 mm. (The largest diameter of one of the 

 cement-glands of Balanus improvisus is not quite - 2 mm.). The interior of the cells 

 is filled with a plasmatic mass, which shows the curious property of staining rather 

 intensely with aluminium carmiuate. At the same time, the large nucleus, which 

 occupies nearly the centre of the cell, and which measures half the length of the cell 

 itself, is coloured also and much more intensely. In many preparations the body of 

 the cell shows an extremely delicate granular structure, whereas the nuclei arc coarsely 

 granulated, or appear to have a fibrillar structure. In Lcpas nucleoli have not 

 yet been observed. PI. II. fig. 5 shows the condition of the cement-cells in the 

 Cypris-larva. I do not quite understand in what way the pear-shaped -land 

 develops from these cells. The size of the latter is about 0'03 mm., at least in the 

 case of Lcjxts australis. Towards one side, and as a rule in the longer axis of the 

 cell, its wall is produced so that the cell assumes the shape of a pear ; this produced part 

 slopes into a long and narrow duct (PI. V. fig. 5). The structure of this duct is very 

 simple ; here and there small cells are visible in its wall (measuring about 0'005 mm.), 

 which on the exterior is lined by a kind of thin cuticle. 



The ducts of the different cement-sdands unite together to form a much more 

 capacious duct; a little before the place where the junction is observed, a transverse 

 short duct often runs from one branch to the other; all the ducts together form an 

 irregular network, the thickest branches finally pour out their contents into two 

 longitudinal ducts. The ducts (fig. 5, d), which communicate directly with the glands, 

 have a diameter of about 0"025 mm. ; the two longitudinal ducts in which the 

 contents of the narrow ducts are evacuated, measure about 0"05 mm. in width. In a 



1 P. P. C. Hoek, Zur Entwickelungsgeschiclite der Entomostraken, 1. Embryologie von Balanus, NiederlUnd 



Archie f. Zool., BJ. iii. pp. 47-82, 1876. 



