OF MASSACHUSETTS. 19 



many conspicuous gland cells (glc). Between it and the follicles of the 

 generative gland is a thick layer of connective tissue, extending in between 

 the follicles. The follicles of the ovary (ov) are not so regular in outline 

 when seen in section as those of the testis (t). The walls of the latter 

 bear a follicular epithelium (fep). In the ovary, the cells of this layer are 

 in all stages of development into eggs. The eggs themselves, crowding 

 the follicles, possess a very thick membrane and their protoplasm is finely 

 granular. A duct from the follicles is seen at d. 



The mother cells of the spermatozoa (fep) are circular and of constant 

 size in the follicles of the testis (t). As we follow the mass of cells inward 

 from these mother cells they become very gradually smaller and smaller, 

 until their final divisions result in the spermatozoa. They are so arranged 

 that their " tails," in forming, project in extended masses toward the lumen 

 of the follicle and give it a radiating appearance. I have not been able 

 to determine how many times a mother cell divides in forming spermatozoa, 

 for the cells are all rounded and give no evidence of their divisions, as 

 they do in the testes of many animals. A duet of the testis containing 

 spermatozoa is shown at d. The ducts of both testis and ovary are com- 

 posed of slightly columnar, ciliated cells. In the wall of the duct of the 

 testis is shown a single deeply stained cell, which is evidently a gland cell. 



CHAPTER III. EARLY LIFE HISTORY. 



The Ripening of the Reproductive Organs. In the early spring the 

 sex products of the scallop begin to ripen, as the eggs and spermatozoa 

 mature preparatory to the summer spawning. The final ripening takes 

 place during the month of May, when the water has reached a tempera- 

 ture ranging from 45 to 50 F., and the scallop is prepared "to shoot 

 its spawn " in the first part of June. During the month of May the 

 generative organs take on a plump appearance; the eggs grow larger; 

 the spermatozoa become active; and the ovary passes from an indis- 

 cernible pink to a deep orange color. This change in color furnishes 

 a general index for recording, by the aid of color charts, the spawning 

 period of the scallop. 



The Egg. The egg or female cell (Fig. 1) is a small spherical body 

 surrounded by a thin membrane inclosing a protoplasmic fluid. Lying 

 in the protoplasm are numerous yolk granules which give to the egg an 

 opaque appearance. These granules form the nutritive part of the egg. 

 The shape of the mature egg when extruded appears spherical, but, 

 when measured, one axis will be found slightly longer than the other. 

 If the eggs are cut from the ovary they have a variety of shapes, due 

 to the manner in which they were compressed within that organ (Fig. 

 3). The scallop egg resembles that of the clam and oyster in size, the 

 average diameter being about 3 /ioo of an inch. In the ovary the eggs, 

 when mature, have an orange color, and when discharged " en masse " 

 still retain that color ; but when separated appear, to the naked eye as 

 minute white specks. The color intensity of the mass seems to be due to 



