igii'.] F. H. Stewart : Development and Anatomy of Cirripedes. 43 



by the formation of two grooves, and their separation from the wall of the duct, in 

 the same way as the notochord is formed from the gut of vertebrate embryos. 



In an adult measuring 5 mm. the young ovaries resembled those of the 25 mm. 

 specimens, but were larger and more clearly marked off. In specimens measuring 

 10 mm. they were still longer, but were still fine unbranched solid cylinders. 



In a specimen measuring 12 mm. (pi. vi, fig. 3) the tubes are also still single. 

 They run through the upper quarter of the peduncle, and in the lower portion of their 

 course are no longer embedded in the wall of the rostral duct. The distinction 

 between ovary and oviduct has also appeared. In the lower ovarian portion the 

 cylinder is definitely solid, and the nuclei are central : in the upper oviducal portion 

 there is a rudimentary lumen, and the nuclei are peripheral. 



The tube measures -035 mm. in diameter, the nuclei -005 — -qi mm. 



In a 16 mm. specimen they have practically reached the adult form, an oviduct 

 runs along either side of the rostral duct, and ovarian tubes branching through the 

 peduncle below the cement glands. At the fundus of an ovarian tube (pi. vi, fig. 4) 

 inside the outer enveloping membrane (gc.n.) there is still the syncytium The 

 nuclei lie somewhat peripherally, almost identical in character with those of the 

 2'5 mm. specimen, but with larger nucleoli. Young ova (-04 mm. diameter) with 

 abundant protoplasm, large vesicular nuclei ("015 mm.) with a single large spherical 

 chromatin mass (005 mm.), are found close to the fundi of the tubes (pi. vi, fig. 5). 



In the mature hermaphrodite the ova can be classed in two stages : (i) without 

 yolk,^the protoplasm vacuolated, the nucleus as in the 16 mm. specimens, except 

 that it often contains a second smaller chromatin mass ; minute nuclei are found in 

 the protoplasm of the cell identical with those of the epithelium of the tubes ; ' (2) 

 large ova crowded with yolk (pi. vi, fig. 6). 



It will be noticed that in the course of its development the rudimentary ovary 

 grows both upward toward the prosoma to form the oviduct and downward and 

 inward into the peduncle to form the branching ovarian tubes. 



(6a) In consequence of Gruvel's statement that he had found a rudimentary 

 ovary in the male of Scalpellum peronii I carefully examined several dwarf specimens 

 (males) of Scalpellum squamuliferum in various stages of development to ascertain if 

 any trace of a rudimentary ovary could be discovered in this species. The specimens 

 were very well preserved, and the sections were extremely good and complete, but no 

 trace of such an organ could be found. It might be expected that, if such an organ did 

 occur in the male, it would resemble the ovary of the hermaphrodite in one of its earlier 

 stages of development, and would occur in the same situation. For this reason parti- 

 cular attention was given to the walls of the rostral duct, but not even the slight 

 accumulation of nuclei at the two sides of the duct which occurs in the pupa of the 

 hermaphrodite could be found. Nor could I find any cells of the character described 

 by Gruvel (7, p. 121) which did not clearly belong to the cement glands. 



1 Compare Gruvel (7a, p. 439). He regards these nuclei as belonging to unsuccessful ova, which 

 are being consumed by the large successful ones. 



