14 EMBRYOLOGICAL MONOGRAPHS. 
PLATE ITf. 
Development of the Hyprowa, continued. Figures from Louis Acassiz, Grorce J. ALLMAN, 
G. von Kocu, and A. KowALewsky. me 
A. apex. Apex. Opercular summit of gonan- or, Mouth. 
gium. ; om. Ovum. 
B. bi sto. Blastostyle. P. pr, Club-shaped body. 
C. can. ere. Cireular Canal. fh. r, th, Radial tubes. : 
cal. Calyx, ealycle, hydrotheca. T. ta, Tentacles of free or unattached form, 
cav. Cavity. gonophore. — : 
E. eb. Epiblast. . ta!, Tentacles of hydranth. 
ebl. Epiblast of stem. tb, Radial tubes. 
G. ya. Stomach. U. ubr, Umbrella. 
ga. cav. Gastric cavity. y. Perisare, _ 
H. hb. Hypoblast. 6. Perisare of calycle. 
hol. Hypoblast of stem. g.  Ferule-like enlargement of the pedun- 
Sf. man. Manubrium. salts cle of the calycle. 
mem. Membrane. ¢. Spadix of the sporosac. 
O. ocy. Otocyst. 
Figures 1-5, 6-12*, 15, 16, were arranged by A. AGASssIz. 
1-5. Obelia commisuralis, McCr. From Agassiz, op. cit. Vol. 1V., Pl. XXXIV. figs. 13, 13*, 16, 17, 18. 
1-5*. Development of the medusa. 
1. Profile view of a medusa bud just forming on the hydroid. 4. Chymiferous tube. ubr. Umbrella. 
2. End view of a bud of the same age. ¢. Chymiferous tube. : 
3. Two medusa-buds in different stages of growth. eb. Epiblast. hb, Hypoblast. man. Manubrium. — 
tb. Chymiferous tube. whr. Umbrella. : 
4, A medusa-bud, in the calycle, from the blastostyle. eb. Epiblast. hb. Hypoblast. ¢6. Chymiferous tube. 
ubr. Umbrella. 
5. Free medusa (gonophore) as it escapes from the calycle (yiew from below). can. ere. Circular canal. 
man. Manubrium. ocy. Otoeyst. or. Mouth. ta. Tentacle. 
5°. Obelia geniculata, Allm. from Allman, A Monograph of Gymnoblastie or Tubularian Hydroids. Ray Soc., 
1869, p. 35, fig. 10. 
Sexual zodid with ova (om.) budding from the radial canal (r. tb.) ubr. Umbrella. ¢. Spadix of the 
sporosac.” 
6-11. Development of the hydroid head (hydranth). 
6-11. CiytrA porerium, Ag. From Agassiz, op. cit. Vol. IV., Pl. XXVIII. figs. 4, 6, 7, 8, 9. 
These figures show the successive stages in the growth of the hydranth up to the stage (fig. 11) in which 
it approximates the form of the adult. cav. Cavity of the ealycle surrounding the axis. .ca7. Calyele 
(horny cup). ¢%. Epiblast. eb’. Epiblast of the pedicle. ga. Stomach. 1b. Hypoblast. AU/. Hy- 
poblast of the pedicle. 6. Perisare. . 
12*-12*. Development of Zaomedea flexuosa. From Allman, op. cit. p. 72. 
12°-12*. Development of the hydranth. 
12". “ Very early condition, in which the bud forms a simple cylindrical exeal offset from the coenosome.” 
12°. “The distal extremity of the bud has become enlarged, so as to present the form of an inverted cone.” 
