240 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Plate 16. 



tFig. 21. Red female lobster, colored from life. Length llf inches; weight about 2 pounds. Captured 

 in the vicinity of Mount Desert, Maine, April, 1894. An examination of the reproductive 

 organs showed that the lobster had not yet reached sexual maturity. For photograph of 

 this lobster see plate 3. A trifle under one-half life-size. 

 Fig. 22. Adult male lobster, colored from life. Length 10 inches ; weight about Impounds; shell mod- 

 erately hard. Woods Hole, Massachusetts, August 14, 1891. About two-thirds life-size. 



Plate 17. 



Fig. 23. Eggs of lobster showing an unusual color variation. Drawn from life. The embryo was 

 somewhat past the egg-nauplius stage. The lobster, which was 12£ inches long and 

 weighed 2 pounds 5 ounces, was captured at Woods Hole, Massachusetts, December 4, 

 1893, and sent to me alive. These eggs turned a very light salmon-color when boiled. Six 

 times natural size. 



Fig. 24. Cluster of fresh eggs of lobster, colored from life. Laid in aquarium at the United States 

 Fish Commission station, Woods Hole, Massachusetts. Drawn August 11, 1893. When 

 first examined the eggs were closely adherent, and the glue which bound them together 

 was very soft. The ovary of the lobster was examined on August 17; it was of small size, 

 and contained but few unextruded eggs, which were partially absorbed. About 6 times 

 natural size. 



Fig. 25. Cluster of egg embryos from swimmerets of female shown in plate 7. Drawn from life 

 December 7, 1893 The entire mass of eggs are attached to each other and to the seta 1 , or 

 hairs of the swimming feet, as shown in the drawing. A single detached seta with a 

 number of eggs glued to it is here represented. About 13 times natural size. 



Fig. 26. Profile view of embryo released from eggshell; taken from a cluster like that in fig. 25. 

 Drawing made December 12, 1893, after killing the embryos with hot water. Embryos 

 from the same lobster (see fig. 8) lived eight days in damp seaweed, in a cool room, and 

 could apparently have been kept alive under the same conditions for a much longer time. 

 Enlarged 33 times. 



Fig. 27. Side view of embryo, as seen through the transparent shell. Drawn and colored from life. 

 Eggs from same batch as those shown in fig. 25; female represented by plate 7. The 

 conspicuous green yolk, which is restricted to the upper half of the egg, fills the cavity 

 of the mid-gut. This eventually forms the "liver" or gastric glands, the anterior lobes 

 of which are clearly seen in fig. 28. The clear space to the right (on the lower side in 

 fig. 28) represents the heart. Below it the intestine joins tne mid-gut. The eye is shown 

 as it appears in reflected light in fig. 27, as in transmitted light in fig. 28. (See p. 169.) 

 Enlarged 33 times. 



Fig. 28. Dorsal view of embryo shown in fig. 27. Enlarged 33 times. 



Plate 18. 



Fig. 29. Lobster hatching. Drawn from life July 5, 1891. The membrane of attachment (secondary 

 egg membrane) has split along the middle line and is being drawn off over the head. The 

 inner part of the shell (primary egg membrane or "chorion") invested the embryo as an 

 exceedingly delicate, transparent membrane, and was ruptured (above the eyes) by needles 

 in order to show it. When the outer membrane is borne away it usually drags the deli- 

 cate inner one with it. Enlarged 33 times. 



Fig. 30. Lateral view of a lobster, teased from an egg which was about ready to hatch, to show the 

 embryonic cuticle which must be shed before the first swimming larval stage is reached. 

 The healthy embryo sheds this skin either at the time of its escape from the eggshell or 

 very soon after it. The intestinal concretions are clearly seen in both this and the pre- 

 ceding figures. The pigment cells of the skin and other details are purposely omitted. 

 Drawn from life. Enlarged about 33 times. 



Fig. 31. Profile view of lobster in fifth stage. General color reddish-brown. Pigmentation of skin 

 not represented. Rudimentary exopodites of thoracic appendages present. Length 

 16 mm. July 2, 1891. Enlarged 9 times. 



