316 J. H. OETON. 



RATE OF GROWTH IN SOME PLATYHELMINTHES. 



Among the Platyhelmia strong indications have been obtained that 

 Cycloporus, Leptoplana, and their allies pass through a generation 

 within a few months, but no certain evidence has been obtained with 

 regard to these animals. The results will be more fully discussed later. 



RATE OF GROWTH IN SOME ANNELIDA. 



A good deal of information has been obtained of various members of 

 the Annelid group, and especially of the sedentary Polychsetes. Pomato- 

 ceros trigueter and Hydro ides norvegica grow to nearly full size in about 

 4 months, and at this age the former has yielded in many cases practi- 

 cally 100 per cent of embryos on being artificially fertilized, while a 

 specimen of Hydroides of the same age shed ripe eggs, but unfortunately 

 no male of the same age was available for a fertilization. The common 

 species of Filograna has been obtained, carrying ripe eggs and trocho- 

 spheres at an age probably less than four months, having gTown through 

 the summer. About the same time another experiment yielded speci- 

 mens with fully developed eggs at an age not greater than 10 weeks and 

 4 days. Later in the year full-sized specimens with buds had an age 

 not greater than 4 weeks and 2 days. There can be little doubt, therefore, 

 that in this species there is an alternation of generations, the summer 

 forms producing eggs and sperm and the autumn and winter ones 

 producing buds. 



Polynmia, Dasychone, and many others have been found to attain 

 a good size in much less than a year. Ripe Serpula vermicularis not 

 more than about 10 months old yielded an excellent result on being 

 fertilized. Dinophilus has been reared through at least one generation 

 in the Laboratory within a period of 7 weeks, and Ophryotrocha to a 

 medium size in 8 weeks, but with more attention doubtless the rate of 

 growth in these two forms might easily be found to be twice as great. 

 Chsetopterus at an age less than 13 months grew a tube 14 cms. long and 

 had developing ova in its gonad, and Sabella fcivonina a tube 12-6 cms. 

 long in less than 31 weeks, and at this age contained well-developed but 

 not quite mature ova. Similar results have been obtained with many 

 f^ee-li^^ng Polychsetes, but these will be discussed later. 



RATE OF GROWTH IN SOME POLYZOA. 

 One interesting result has been obtained among the Polyzoa. By 

 continued experiments and observations Bugula flabelhkt* was found 



* Including Bugula calaihus, Norman, for the purpose of the present paper. 



