THE AMERICAN LOKSTER. 



43 



(lining the latter half of July and the first two weeks ot August. The summer 

 spawning of each year lasts about six weeks, but may fluctuate from year to year, 

 backward or forward through an interval of a fortnight. 



The observations for the years 1890 and 1891 only, are large enough to make a 

 comparison of much value. Of the 8G lobsters with new eggs examined in July and 

 August, 1890, 81 per cent extruded eggs in July and 15 per cent in August, while in 

 the following year, out of 38 females, one-half had laid in July and half in August. 

 In 1890, however, 72 per cent of the eggs were laid in the latter half of July and 15 

 per cent in the first half of August, while iu 1891 47 per ceut were extruded in the 

 first part of August and 31 per ceut in the latter half of July. The season of 1891 

 thus appears to have beeu somewhat later than that of the former year. 



The record of ocean temperatures given in table 2 (p. 25) shows that the water 

 was cooler in 1891 than iu the preceding year, the difference of the mean annual 

 temperatures being 1.6°. This difference is slightly raised by eliminating the mouth 

 of June, when the smallest number of lobsters carry eggs. It is possible that so small 

 a variation as is here recorded in the mean annual temperature of the sea water woidd 

 sensibly affect the rate of development, yet a larger number of observations would be 

 required before this could be satisfactorily shown. 



There are undoubtedly other causes than the temperature changes which influeuce 

 the growth of the ovarian eggs, which it must be remembered require at least two 

 years to reach maturity. Anything which affects the individual during this interval 

 may affect also the time of spawning, and this affords a partial explanation of the fact 

 that eggs are sometimes produced at other seasons of the year than the summer. 



SUMMER EGGS ON THE COAST OF MAINE. 



Tables 8, 9, and 10 throw more light on the time of spawning upon the coast of 

 Maine, where the water is somewhat cooler than at Woods Hole. The range of tem- 

 perature in the Gulf of Maine is about the same as that obtained at Pollock Eip 

 light- ship, off the southern end of Cape Cod, namely, 32° to 62° F. 



Table 8. — Time of spawning at Southport, Maine. 

 [Many of the lobsters were captured in Nova Scotia and brought to Southport before laying their eggs.] 



No. 



1 

 2-3 

 4-8 

 il-10 

 11-16 

 IT -Jl 

 22-23 

 24-25 



Place of spawning. 



Southport, Me 

 do 



.do 

 .do 

 .do 

 .do 

 do 

 do 



Date of 



exami- 

 nation of 

 eggs. 



1893. 

 Sept. 7 

 ...do.... 

 ...do .... 

 ...do .... 

 ...do.... 



do .... 



.do .... 

 .do .... 



Stage of development. 



Days. 

 61 

 35 

 33 

 30 

 29 



Eye-spot, linear 27 



Before formation of eye pigment 25 



Egg nanplius, late stage 18 



Telson in front of optic lobes : Eye-spots oval . 



Eye-spots lenticular or nearly semicircular 



Eye-spot narrower than in X'os. 2-3 



Eye-spot, small crescent 



do 



of em- 

 bryo. 



Date of 



extrusion | 



of eggs. 



July 8 

 Aug. 3 

 Aug. 5 

 Aug. 8 

 Aug. 9 

 Aug. 11 

 Au;r. 13 

 Aug. 20 



