THE REPRODUCTIVE PERIOD IN THE LOBSTER. 
163 
which serve as a handy and convenient chronometer. The ratio of growth in stages 
1 and 2 can also be determined. The volume of the laid egg in the final stage is also 
known, so that it only remains to ascertain the time interval between stages 2 and 3. 
Pig. 4. — Series to illustrate the growth of the ovarian eggs during first year after spawning, (a) Ovarian egg 
in initial stage as shown in Fig. 1. ( b ) Ovarian egg fifteen days after egg-laying. External eggs borne on 
the swimmerets, in “nauplius” stage. Radius, 8.6 mm.; contents, 2.67 c. c., August 6. (c) Ovarian egg 
forty-two days after egg extrusion, the age being determined by state of development of attached ova. 
R. 12; contents, 7.22 c. c., August 21. ( d ) Ovarian egg, after approximately one year from egg-laying, average 
of ten ova from lobster taken June 19, 1900, with external egg ready to hatch. R. 16.2; contents, 17.77 c. c. 
The relative volumes of the ovarian eggs at these successive periods are as fol- 
lows: 0.77 c. c., 11.71 c. c., 136.07 c. c. Accordingly, during the first, period of 
growth the ova increase in volume fifteen times, or the ratio of growth may be 
expressed by I : 15. Upon the theory of biennial spawning we should expect the 
ratio of growth for the second period to be approximately the same. The values 
Fig. 5.— Series illustrating the growth of the ovarian eggs during the second year after spawning, (a) Ova- 
rian egg one year ten months after egg-laying. The female from which this ovary was taken was kept 
in a floating car from June 19, 1900 (period of hatching), until May 1, 1901. Radius 17.9; contents, 23.97. 
( b ) Average size of two fresh ova, taken August 19. These eggs were soon to be laid as shown by their 
size, color, and general appearance ot ovary, (c) Unextruded ovarian eggs, taken about three days after 
egg-laying. The external eggs were in segmentation. Radius, 27.1; contents, 83.19 c. c. 
given above, for which only a relative degree of accuracy can be maintained, give 
this ratio as 1 : 12. This result supports the conclusion that the ovarian ova which in 
spring following the last ovulation attain the size shown in tig. 2, experience a second 
period of rapid growth and are laid during the following summer. This is rendered 
