326 J. H. ORTON. 



It is interesting that tlie maximum rate of growth in this group occurs 

 at about the same time of the year as that found in the Sycons, some 

 Polyzoa, some Molluscs, and some Hydroids. This period of maximum 

 rate of growth occurs about August and September, and it is hoped that 

 when the whole of the material collected has been worked out that it will 

 be possible to estimate more accurately the rate of growth for different 

 times of the year in all the groups. 



EATE OF GROWTH IN SACCORHIZA BULBOSA. 



A few marine algse have been collected in the course of the experiments, 

 and so far the most interesting growth obtained is that of Saccorhiza 

 {Laminaria) bulbosa, which between April and October, a period of 7 

 months, was found to grow a lamina 3 to 5 feet long and a sub- 

 spherical base about 5 inches in diameter. 



SUMMARY. 



From the foregoing preliminary account it will have been seen that 

 the rate of growth and the period of the life-cycle in marine invertebrates 

 are in many cases much more rapid than has hitherto been suspected. 

 Many forms which have been generally considered annuals with one 

 breeding period, such as the Sycons and other Porifera, some Polyzoa, 

 some Ascidians, some Molluscs and some Annelids, have been shown 

 to pass through two generations, and in many cases there are strong 

 probabilities that they may pass through more than two genera- 

 tions in a year. Even among the Hydroids the rate of growth is probably 

 greater than has generally been suspected. 



The results obtained will be discussed in relation to those obtained 

 elsewhere, when the whole of the scattered literature on this subject has 

 been gathered together. So far, however, very few reliable observations 

 have been found on the rate of growth in marine invertebrates, as indeed 

 Weismann* has already noticed, and I should be very glad to receive 

 any references to work of this kind that readers may have come across. 



* A. Weismann, Essays upon Heredity, Vol. 1, p. 57. Edited by E. B. Poulton, S. 

 Schbnland, and A. E. Shipley. Oxford, 1891 



