366 BULLETIN OF THE BUREAU OF FISHERIES. 



While we can not make direct comparisons with confidence without knowing the 

 number of individuals in each case concerned, figures which neither Smith nor Hadley 

 give, I am inclined to believe that while the rate of growth for Woods Hole lobsters 

 during their earlier stages may be greater than 15.3 it is less than 18 per cent, and that 

 while my former estimate of the age of a lo-inch marketable lobster to be from 4X to 5 

 years may need the addition of a plus mark, especially in the female, it is probably not 

 far from the truth. 



Female lobsters are found bearing eggs for the first time when measuring from 7>< 

 to 12 inches (18.5 to 30.5 cm.). Amid limits so wide it is impossible to say at what 

 time the average female lobster reaches the reproductive age, but it is probably not far 

 from the lo-inch length, which according to Hadley would represent the twenty-third 

 molt and an age of about 6}4 years. We have no data upon the time of sexual maturity 

 in the male, but should expect that it would be reached at the same or at a slightly 

 earlier period. 



Regarding the questions of rate of growth in Homarus gammarus of Europe, I shall 

 give the general conclusions of Ehrenbaum (^7), whose studies at the Helgoland laboratory 

 are well known : 



It is possibly not superfluous at the end of these observations to state again clearly that the resvlts 

 which the American naturalists and we in reliance upon them have reached in regard to growth and the 

 relations between size, age, and life-stage cannot be regarded as completely reliable. 



The numerical results which are given in the works referred to and which have been partly repro- 

 duced, can in the most favourable cases be regarded as of only average value, especially when we reflect 

 that all biological relations possess a certain variability and cannot be expressed in absolute figures. 



Ifr moreover, we reach the result that the Helgoland lobster lays her eggs for the first time in her 

 seventh year of life, it by no means contradicts the idea that in many individuals this may happen 

 in the sixth year, while occasionally females of only 23 centimeters {g}i in.) in size have been observed 

 with extruded eggs, and moreover it may happen that in single cases the first egg-laying is delayed 

 until the eighth year of life. 



But even disregarding this natural and anticipated variability, it cannot be denied that otu" figures, 

 even as averages, possess a certain untrustworthiness, since only one element rests upon direct observa- 

 tion, while another is based upon combinations. This uncertainty is sufiiciently reflected in my earlier 

 contributions (see communication of 1903, p. 154), wherein I came to the conclusion that female lobsters 

 were in their sixth year of age when for the first time they carry eggs, while now, standing upon a basis 

 not much more extended, I have accepted the seventh year in preference. 



Moreover the American authors waver between the sixth and seventh year as regards the period in 

 question, and find a way out on the supposition that the period is six years for the southerly state of 

 Rhode Island, and seven years for more northerly Massachusetts and Maine. Accordingly it is well to 

 lay it down as a general rule that the first egg-laying takes place in the sixth or seventh year of life, 

 with the higher probability favoring the longer perio'd. This statement would then hold good for both 

 American and European lobsters throughout their areas of distribution. Moreover, it can be accepted 

 as fixed that this egg-laying takes place in from the twenty-third to the twenty-fourth stage of life. 



