170 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



occurs. I cannot therefore agree with Kingsley ('89, p. 30) in saying 

 that Grobben " showed that the gland belonged to the mesodermal 



tissues." 



Ishikawa ('35, p. 422, PI. XXVIII. Figs. 68, 90-94) finds in Atye- 

 phira, in the base of the second antenna at the time of the appearance 

 of the first pair of maxillipeds, a circular group of about eight granular 

 ectodermic cells. In these is formed a cup-shaped depression from the 

 exterior, which has a large mouth and grows deeper while the opening 

 narrows. " The cells which are concerned in the formation of it [the 

 antennal gland] are all ectodermic." By the time of hatching, the de- 

 pression has become a canal having three or four convolutions and filled 

 with granular fluid. 



Iieichenbach ('86, pp. 97, 98) sees in sections of the embryo of Astacus 

 with well outlined maxillipeds (Stage G) the Anlagen of the glands ap- 

 pearing in the basal segment of the second antennae as recently formed 

 plugs of ectoderm (Taf. X. Fig. 125 u. 126, g. D.). The arrangement 

 of cells shows that a sac is to appear, although no lumen is as yet present. 

 At a slightly older stage (Stage H), with pereiopods marked off, surface 

 views show a crescentic arrangement of cells bordering an involution. 

 The opening of the ectodermic invagination is the permanent mouth of 

 the gland. This invagination grows anteriorly, making a slight turn. 

 The Anlage remains in connection with the ectoderm, and at first does 

 not even approach mesodermic tissue. At later stages (Stage J, with 

 distinct pleopods, and Stage K, with strongly developed eye pigment) 

 flat connective-tissue cells begin to surround and soon envelop the gland 

 (Taf. XIII. Fig. 205). 



Thus far, with the exception of the unsupported statement of Grobben 

 ('80), there is a consensus of opinion as to the ectodermal origin of the 

 glands. 



With this opinion Kingsley disagrees. He found ('89, p. 29, Plate 

 II. Fig. 49) in Crangon vulgaris a patch of mesoderm stretching into 

 the base of the second antenna as a solid plug at a stage when the 

 eye pigment existed as a crescentic line (Stage G). In a somewhat 

 older embryo (Stage H) "a cavity (Plate II. Fig. 61) appears in this 

 tissue, and the cells lining it take a well marked epithelial character, 

 their boundaries being distinct." At no " stage does the green gland 

 have any connection with any other cavity within the body. . . . The ex- 

 ternal opening to the gland is not formed until after hatching." By this, 

 I infer, is meant the confluence of the lumina of the endsac and the duct. 

 The mesodermal origin of the antennal gland in Crangon agreed with 



