PLATE II. 

 OVIDUCT OK CHIMERA COLLIBI AND MODE OF FORMATION OF THE EGG-CAPSULE. 



(All figures natural size, excepting the last, fig. n.) 



a. I. Line in which the lip of the operculum separates m. Rudiment of mesentery of gut containing ves- 



from the side of the capsule. sels. This lies behind oviduct (cf. plate i, 



b. Blastoderm. figs, i and 4). 



c. Aperture (cervix) through which the anterior end of m. o. Mesovarium. 



the capsule is beginning to protrude. o. Ovum about to break from the ovary. 



e.g. Capsular gland. In this region a series of trans- ovd. Oviduct. 



verse zones can be made out extending as far ovd. a. Oviducal artery, 



posteriorward as t. o. ovd. s. Oviducal sinus. 



c. p. Foldings in the margin of the capsule in which r. Folds in groove of lateral web by which the 



later appear the perforations in the caudal rugae of the capsule are established, 



sheath. s. Stigma. 



d. k. Groove in which dorsal keel of egg-capsule is laid t. o. Folds under the edge of the lime gland in which 



down. At either side of this are thickened the terminal organ of the filamentous capsule 



areas which form the dorsal wall of capsule. is laid down. 



/. iv. Folds in oviduct, in which the lateral web of the t. s. Thickened area in which is molded one side of 



capsule is laid down. the tail-sheath. 



Fig. 5. Ovary and oviduct of left side, showing egg about to be taken into the oviduct. The ovary 

 is closely enveloped in the mesovarium, m. o., the fold of which is continued back, encloses 

 the oviduct and shows at ovd. s. the beginnings of the oviducal sinus. It will be observed 

 that the egg, o., about to escape from the ovary, is of great size. This is due to its fluid 

 consistency at this stage, its contents having spread out when the preparation was made. 

 A conspicuous stigma is present, to which nutrient blood-vessels converge. At this stage 

 the oviduct is situated close to the dorsal wall of the cavity of abdomen. In later stages, 

 during growth of the capsule, the oviduct hangs down freely into the abdomen and is 

 bathed by the blood in the enlarged sinus, ovd. s. 



Fig. 6. Preparation of oviduct from which a developing capsule was removed, showing the fold" 

 ings of the lining membrane which serve in modeling the capsule. 



Fig. 7. Preparation of anterior end of oviduct, showing a portion of the egg-capsule in situ. This 

 figure illustrates the segmental" character of the capsular gland, for each segment of which 

 vessels are provided by the oviducal artery. The narrow end of the egg-capsule is shown 

 within the oviduct ; at c. p. foldings are shown in its marginal walls, which later produce 

 the perforations of the caudal sheath. At either side of the deep groove, d. k., in which 

 the dorsal keel of the capsule is molded, appears a mass of glandular tissue. This is out- 

 rolled on either side into the marginal creases in which the lateral web of the capsule is 

 being laid down. 



Fig. 8. Immature capsule containing egg. The tail end of this capsule was incomplete, but by 

 means of a ligature it was so preserved that the egg was incubated. By the tension of the 

 ligature, however, the shape of the capsule was somewhat altered and the egg became more 

 spherical in form. The lateral web of this capsule is delicate and extremely wide. 



Fig. 9. Egg-capsule opened, showing shape into which the egg is elongated during incubation. 



Fig. 10, Egg-capsule at about the time of deposition, defective only in its terminal filament. This 

 was, in fact, deposited while the fish was in captivity. From this figure one obtains an 

 idea of the translucency of the freshly deposited capsule. 



Fig. ii and Fig. 11 a-c. Details in structure of egg-capsule. Fig. n shows a detail in the struc- 

 ture of the opening valve. The fold in the wall near apex of capsule, a. /., passes 

 upward and inward into a ridge, the walls of which are folded into thickened and thinner 

 areas alternately. At a. a transverse section shows height of this ridge. At /'. appears a 

 lateral view of the same ridge, indicating how it is made up of alternating elements. By 

 a process of weathering in the thin intervening areas fenestrae are formed which insure 

 respiration and which later, by a continued process of weathering, break open the valve of 

 the capsule. In fig. 11 c. is shown the continuation of this folding process, occurring at 

 sides of tail region of capsule. By the weathering of the thin spaces between the folds res- 

 piratory openings are gradually formed. 



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