THE OSTEACODA. 



of the line are the successive products, by an emi^irically-t'ouucl growth-factor, of 

 starting from I'SO, the lowest observed mean of the series *. 



281 



means 



The close approximation of the two sets of means — those which seemed to come out 

 of Mr. Waddington's observations, and those got by multiplication with a growtli- 

 factor — seems to show that the inferred grouping was aj)proxiinately correct, and that 

 numerous and delicate measurements would show the validity of Brooks's law at the 

 earlier stages. The drop in the growth-factor is interesting, if genuine. 



But while the species as a whole thus seems to fall into general line with the 

 observations on Ostracods, the individual specimen (as was also noticed in the American 

 Lobster) does not seem to follow the law with mathematical exactness at each moult. 

 An individual of, say, the mean breadth at a particular stage will not necessarily be of 

 the mean breadth of the subsequent stage ; it may be either broader or narrower, so 

 long as it keeps within the extreme limits for that stage. In Mr. Waddington's 

 observations the actual increment at a moult (=tl)e broader -=- the narrower) varies a 

 good deal in some cases. To some extent this may be due to variations in tlie aquarium 

 conditions : a large part is probably due to the specimens having been dried before 

 measurement f ; part may be set down to the method of measurement (compass and 

 scale, not micrometer-microscope) ; but a part is probably the animal's own " error." 



A most interesting piece of work awaits anyone Avho will take uj) the whole question 

 on large Crustacea, with refined systems of measurements of wet specimens. On the 

 Avhole, a form in which the total length was easily measux'able would probably be more 

 reliable than a Brachyuran, in which the breadth of the cephalothorax might possibly 

 be intiuenced by the necessity for housing a rapidly increasing generative organ at a 

 certain stage. 



General Course of I he Development o/' JLlalocypridte. 



It will have been obvious to those who have followed the descriptions in the 

 Systematic Bart, that the morphological changes in the successive moults proceed along 

 fairly well-marked and similar lines in all the species. It is too early as yet to lay 



* Below 5 mm. tho observations are numoioiis, but the measurements not delicate enough to separate the various 

 groups ; above 'S,'> mm. tho obsoivatious arc tew and widel)- scattered. 



t Ke-moasuremcnt of some of Mr. Waddingtou's series iu the ijritish Museum seemed to show that they had 

 shruuk even siucc ho measured them. 



