126 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



What is the function of these organs which are distributed so widely over the 

 surface of the body? It has been found that glands of a similar character play a part 

 in excretion. (Text-book of Comparative Anatomy, Lang, part i, p. 330.) Those found 

 in the oesophagus were regarded as salivary glands until the embarrassing fact was 

 discovered that they were also found in the walls of the intestine. When occurring 

 in the swimmerets and ventral abdominal region of the female these organs have been 

 considered responsible for the liquid glue or chitin-like cement which is poured over 

 the eggs at ovulation, and have been accordingly called cement glands. It seems 

 probable that they have such a function, and I shall proceed to describe them in 

 detail as they occur in the lobster. 



THE CEMENT GLANDS. 



If we strip off the hard cuticle from the pleopod of a female lobster just before the 

 eggs are laid (fig. 144, plate 40), we will see thousands of opaque whitish bodies lying 

 upon the strands of muscular tissue. Each is a gland not more than an eighth of a 

 millimeter iu diameter, and each opens to the exterior by a capillary duct which 

 pierces the cuticle. The grounds for attributing a cenient-producing function to these 

 organs lie chiefly in their periodical changes coincident with the sexual condition of 

 the female, and in their absence or restricted occurrence in the pleopods of the male. 

 Their position upon the swimmerets also favors such a view. We can not look else- 

 where for such an organ, unless it is to the oviducts, and I know at present of no 

 evidence showing that the latter possess this function in the macrura. 



CEMENT GLANDS IMMEDIATELY BEFORE OVULATION. 



As the time of oviposition draws near, the swimmerets of the female become 

 more and more opaque, especially along the free margins of their branches. At this 

 time a milky-white substance can be pressed out, upon removing the cuticle. This is 

 analogous to what Lereboullet observed in the crayfish (120), and is composed of the 

 glandular tissue. 



At this period the glands have the appearance shown in plate 49, fig. 212. Stained 

 with the Ehrlich-Biondi auilin mixture the cells have a cloudy, granular appearance. 

 Their peripheral ends contain a coarser material, which takes a deeper red than the 

 central parts; the latter appear much lighter, and select and hold some of the green. 

 The distribution and appearance of the zymogen granules may be compared to that 

 seen in the pancreas of a well-fed dog, or the resting cells of the submaxillary gland. 



An attempt to get a secretion from these glands while in this condition by stim- 

 ulating the nerve cord by induction currents was not successful, possibly owing to the 

 fact that these organs had not quite reached the stage of their periodical activity. 



THE CEMENT GLAND IMMEDIATELY AFTER OVULATION. 



The structure of the exhausted gland, taken shortly after the eggs are laid, is 

 illustrated by fig. 211, plate 49. If this is compared with fig. 212, which is treated in 

 the same way, we will find a marked difference in its cytological condition. A very 

 conspicuous zone of deeply stained zymogen granules surrounds the central rosette, 

 while the outer parts of the gland cells are poor in zymogen and stain but feebly. 

 This central darker zone is very variable in breadth, being sometimes reduced to a 

 thin circle, involving only the apices of the cells, and is often very sharply marked 



