WAITE : ANTENNAL GLANDS IN HOMARUS AMERICANUS. 179 



ectodermic sac (of. Fig. 30, Plate 3). After communication is established, 

 an abrupt transition in the character of the wall is still noticeable at the 

 point of union. This level may be termed the mes-ectal line, since it is 

 the line of junction of the mesodermic with the ectodermic part of the 

 organ. There is a valve-like flap of cells projecting from the wall of the 

 cndsac into the orifice connecting the two cavities. This condition is 

 still evident in the first larva (Plate 6, Fig. 51, vlv.). 



The brood of this female kept in confinement during the winter was 

 hatched 33 days after the killing of the specimens which showed con- 

 necting lumina (about 330 days after fertilization), so that when the end- 

 sac comes into communication with the exterior the embryo has already 

 passed through ten elevenths of its embryonic period. It is possible that 

 the establishment of the communication between the two sacs occurs in 

 the earlier part of the period embraced between the ages of 273 and 303 

 days, but even if it does not occur until the latter part of the period, 

 the lumen of the endsac is in direct communication with the exterior at 

 least a month before the end of embryonic life. The only records that I 

 find of the time when this connection is effected in other Crustacea is 

 that made by Allen ('93, p. 338) for Pala3monetes, and by Kingsley ('89, 

 p. 30) for Crangon. Kingsley states that "the external opening to the 

 gland is not formed imtil after hatching." Allen says that the forma- 

 tion of the lumen of the endsac and its communication with the exterior 

 occur early in larval life. In Homarus, however, the lumen of the end- 

 sac communicates with the outside world late in embryonic life. If, as 

 Allen thinks, the establishment of this condition marks the beginning of 

 functional activity, then the antennal gland in the lobster is functional 

 as an embryonic organ. But I cannot agree with Allen. On a priori 

 grounds we may expect an excretory organ in the lobster embryo. Ex- 

 cretion takes place in many yolk-bearing embryos, and special embryonic- 

 organs having this function occur in many cases, such as the embryonic 

 nephridia of Annelids and pulmonate Gasteropods, and the shell gland in 

 the embryo of many Crustacea. In some decapod Crustacea the shell 

 gland is functional in the embrj^o, but atrophies soon after hatching. 

 Whether it is present in Homarus I am unable to say ; but I believe it 

 probable that excretion in the embryo is performed by some such special 

 organ rather than by the antennal gland, for in the latter I find no direct 

 evidence of excretory activity during embryonic life. The cavity of the 

 gland contains neither a granular clot nor excretory globules, such as are 

 found in the larval and adult stages, nor have the cells of the wall of the 

 ectodermic sac the marked striation which is seen later when glandular 



