REPRODUCTIVE SYSTEM AND SEXUAL SUCCESSION OF L. BULIMOIDES 189 



Of the histology of the glandular genital tract, which was not within the scope of Hsiao's paper, 

 only a brief description is needed here. The epithelium of the albumen gland (Fig. 13 a) reaches 

 c. 50 fi in height at stage 6. Its free surface becomes rather ragged by the discharge of secretion and 

 only a few cells remain typical and intact, with the rounded tips which represent the usual condition 

 at stages 4 and 5. Ciliated cells are small and interposed at rather wide intervals between the gland 

 cells. Their nuclei are smaller and darker than those of the glands, and the tufts of fine cilia become 

 dislodged and carried away at the secreting stage. The nuclei of the gland cells are 6-7 /x in length, 

 densely chromatic and rounded to sausage-shaped. The contents of the cytoplasm bear a considerable 

 resemblance to those in the albumen cells of Ellobiidae (Morton, 1954a). The secretory inclusions 

 form masses of tiny granules of varying but minute size. They stain golden brown with eosin- 

 Orange G, and especially towards the base of the cell they become enclosed in clear, non-staining 

 vacuoles. A group of vacuolated spherules is sometimes found enclosed by a single larger vacuole. 

 The secreting cells of the mucous gland (Fig. 136) increase in size from 20 to 30 ^ at stage 5 to as much 

 as 150^ in the greatly distended gland at stage 6. Their nuclei are basal, in a single row, large and 

 densely chromatic. Here again there is a close resemblance to the Ellobiidae. The contents of the cell 

 stain deep purple with haematoxylin and are granular, and with the change to a secreting state, large 

 ovoid, lightly staining droplets are formed, bulging from the cells into the lumen. The ciliated cells 

 are extremely narrow; they fan out as triangular wedges at the free surface, and their small and dark 

 staining nuclei are either compressed between the gland cells, or flattened closely against the top of 

 a neighbouring cell. 



No eggs of bidimoides were taken in the Benguela hauls, nor does Hsiao give a description of the egg 

 mass. Lebour (1932) has, however, observed the oviposition of British retroversa, and has described 

 and figured the eggs as planktonic, floating in small gelatinous strips with the eggs scattered and widely 

 separated. Each strip measures about 2 mm. in length and 0-64 mm. in breadth and both the matrix 

 (which is obviously the secretion of the mucous gland), and the eggs are perfectly transparent. Some- 

 times the strips are interconnected by a thread-like secretion which is presumably also a product of 

 the glandular female duct. 



The penis, as examined at stage 5, is perhaps the most complicated part of the reproductive system, 

 and Limacina, with others of the thecosomatous pteropods, possesses probably the most elaborately 

 constructed penis in the opisthobranchs. As pointed out by Hsiao this organ is practically independent 

 of the rest of the reproductive system, both in position and in structure. The seminal groove does not 

 continue as a closed tube towards the male aperture at the base of the right wing, but passes forward as 

 the ciliated groove and becomes continuous with the interior of a large ovoid pouch the penial sac, 

 lying in front of the rest of the reproductive organs and bulging into the pallial cavity just behind the 

 head (Fig. 14). It is first visible at stage 4, especially large at stage 5 and lost at stage 6. The penial 

 sac is involuted with a lining wall elaborately ridged and furrowed, and this lining, or a portion of it, 

 constitutes the penis itself when evaginated. There is no muscular papilla traversed by a closed vas 

 deferens as in even the earliest pulmonates. Associated with the penial sac is a tubular prostate gland. 

 This is intricately involved in the folds and furrows of the sac, and the whole structure in the fixed 

 and contracted condition is exceedingly difficult to make out clearly. A good deal can be seen from 

 cleared whole-mounted individuals, but in the absence of living material serial reconstruction is 

 necessary to determine its details. Hsiao does not attempt a description, and in the other Thecosomata, 

 such as the cavoliniids, Meisenheimer gives few details. Bonnevie (1916) provides an account of the 

 penis and its associated structures in Cuvierina, a cavoliniid, and there is a briefly labelled drawing of the 

 penis in longitudinal section in his figure of Cymbulia (1905, Atlas, pi. 13). Vayssiere (1915), figuring 

 the opened penial sac, gives a picture of the folds of the interior without any interpretation. Tesch's 



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