554 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
latter bends inward to reach the common oviduct. The cavity of 
the uterus has increased in size, the lumen of the penis opens to 
the outside and the atrial j^ore has appeared. This is the adult con¬ 
dition, save that the vasa deferentia are not connected with the 
penis lumen. The yolk glands are much larger than before and at 
frequent intervals pass from the oviduct up between the gut lobes. 
No mention has been made in the above of the condition of the ovaries 
and testes, for they have not changed greatly. Both are larger than at 
first, the ovaries with more large ova, the testes with their cavities 
containing spermatids of all sizes. Connecting the vasa deferentia 
with the penis, the adult condition is reached (pi. 12, figs. 33, 34). 
The stages in the development of the atrial organs can be best 
shown by a series of diagrams representing them as seen from the 
side. Figure 57 (plate 19) shows at a the primary cavity in the 
parenchyma lined with epithelium (pi. 16, fig. 45). This cavity 
takes on the shape shown in figure 58 (plate 19) in which the ute¬ 
rus {ii) is indicated and^ the j^osition of the penis shown by an 
irregular fold. The portion which will later connect with the out¬ 
side is also seen. The cavity (pi. 19, fig. 59) assumes more and 
more the contour of the adult atrium by the further development of 
the penis, in which a lumen appears, and the development of the 
common oviduct (co). In later stages the developing oviduct of 
each side grows out to unite with the common oviduct, as shown in 
figure 56 (plate 19), and the penis lumen opens on the free end of 
the penis, but the connection of the vasa deferentia with the penis 
does not occur until considerablv later. 
4 / 
The development of these organs shows that there are two dis¬ 
tinct parts, (1) the germ cells and (2) the accessory organs about 
the atrium. The two originate separately and later become con¬ 
nected with one another. There are laid down two cords of cells 
extending from the ovaries well back into the tail. Anteriorly, in 
the position of these cords, the oviducts appear, while back of the 
atrium the cords remain the same and become yolk glands. So far 
as I can make out, the yolk glands arise as outgrowths of this pri¬ 
mary rod of cells. The organs of the atrium begin as a cleft in the 
parenchyma which gradually becomes differentiated into the several 
parts. The testes, ovaries, and oviducts with the connecting yolk 
glands arise in the same place that they occupy in the adult, save 
that with their increasing size the yolk glands extend up between 
