220 BUMPUS. [Vol. V. 



collapse, though they may be brought back, artificially, to their 

 full size by injecting from without into the oviduct. 



The immature ovary is not only small in size, but lacks the 

 pigment of the adult, being almost colorless. Later it becomes 

 bright yellow, and still later minute dots of green appear in its 

 substance. The green finally predominates, and in the fully 

 mature ovary deep green is the prevailing color, though dots of 

 yellow, possibly the same as those found by Lereboullet ('62) 

 in Astacus, are to be seen. 



After the extrusion of the eggs the ovary loses its color in 

 the main, though here and there dark spots may be seen which 

 on investigation prove to be eggs which were not extruded with 

 their fellows. 



So indicative of the condition of the eggs is the color of the 

 ovary that I have been able to predict with certainty the con- 

 dition of the ovarian eggs, without opening the female, by 

 simply looking down through the transparent tissues between 

 the posterior end of the carapax and the tergum of the first 

 abdominal segment. 



As compared with the ovaries of AtyepJiira described by 

 Ishikawa ('85), the genital organ of Homarus is much more 

 elongated and the eggs relatively smaller, — points of difference 

 which might be made equally well for Astacus as described by 

 Rathke ('29) and Huxley ('80). A further difference between 

 the ovary of Homarus and that of Atyephira is to be found in 

 the " germogen," which in the former Decapod is not distin- 

 guishable externally from the " vitellogen." In this respect 

 Homarus resembles Eupagurus. 



The ovary of the young female throws light on the more 

 complex structure of the adult. It is shown in cross-section, 

 PI. XVI, Fig. 12. Enclosing the whole ovary is a dense but 

 transparent layer of muscle and connective tissue which in- 

 cludes certain openings, the blood-sinuses. At about equal 

 distances from each other these sinuses dip deeply into the sub- 

 stance of the ovary, and send ramifying prolongations between 

 the developing egg-cells (Fig. 10, b.s.). The sinuses and pro- 

 longations are invariably limited at their peripheries, and all 

 contain blood-cells. A glance at Fig. 12 shows that the older 

 egg-cells occupy the outer portion of the ovary, while the 

 younger occupy the central portion. The germogenal portion is 



