I9I3-] Ekendranath Ghosh : Mollusca, I. 219 



gland. Under the low power of the microscope the ovarian portion 

 is seen to consist of thin-walled alveoli held together by connec- 

 tive tissue. The posterior portion of the mass (corresponding to 

 about one- third the length) forms a dead white mass, which extends 

 as a narrow strip for a little distance along the lower border of the 

 gland and terminates in a round end towards the anterior portion. 

 The duct of the gland begins from the lower border of the glan- 

 dular mass and then runs backwards to the dead-white portion 

 posteriori}' ; there it forms a close coil and then emerges from the 

 posterior end of the mass. It then curves upwards and forwards 

 along the upper border of the gland for a short distance, and at 

 last bends downwards on the outer side of the mass to end in the 

 oviduct. The albuminiparous portion forms a narrow strip in the 

 \ipper border of the mass. 



Minute structure. — The ovarian portion consists of thin- walled 

 acini bound together by thin layers of connective tissue. Each 

 acinus is lined by a single layer of flattened cells with disk-like 

 nuclei. Inside this layer are numerous cells, more or less rounded 

 in shape and lying attached to the cells of the wall. These cells 

 are massed together in mullberry-like bunches projecting into the 

 cavity of the acini. The cells have large spherical nuclei with a thin 

 layer of protoplasm round them. The chromatin forms a close 

 network with numerous dot-like nucleoli. Attached to the cellular 

 lining are several ova in each acinus, in different stages of develop- 

 ment. At first they are fusiform in shape, but become spheri- 

 cal when fully developed. The protoplasm is granular with a 

 large spherical nucleus placed in the centre. The nucleolus is a 

 refractile spherical body placed towards one side of the nucleus. 

 The ovum is surrounded on the inner surface {i.e. towards the 

 lumen of the acinus) by a single layer of fiattened-cells continuous 

 with that forming the wall. Each acinus gives rise to a duct which 

 opens into the main oviduct. The acinar duct consists of a single 

 layer of ciliated columnar epithelium with elongated nuclei, 

 surrounded by a thin layer of muscular tissue. The main oviduct, 

 which is coiled to form the dead- white mass, consists of a single 

 layer of narrow, much-elongated cells with very long narrow 

 nuclei. The cells are so closely arranged that even in a very 

 thin section, the nuclei seem to be heaped together at right angles 

 to the surface with very little protoplasm surrounding them. 

 The inner surface of the cells is provided with distinct cilia 

 which are as long as the cells themselves. The inner surfaces 

 of the contiguous cells form a continuous refractile border in 

 section. The individual coils of the oviduct are separated'i^y a 

 thick layer of connective tissue with numerous connective tissue 

 corpuscles. 



The albuminiparous portion of the gland consists of a scattered 

 mass of small acini more or less rounded in shape, and separated 

 from one another by thick layers of connective tissue. The epi- 

 thelial lining of the acini consists of a single layer of elongated poly- 

 hedral cells with large oval or elongated nuclei. The protoplasm 



