222 DR. G. H, FOWLER — BISCATAN PLANKTON : 



important organs required for specific identification (thanks to Miiller's iuvestigatious) are then 

 exposed to view; and the frontal organ should be drawn in situ, to easure a true profile. When the 

 specimen has been identified, the left antenna ii can be pushed back into position and the shells closed ; 

 the specimen is none the worse for the operation. For the determination of sex it is better to turn 

 back the left shell than the right, as the penis lies on the left side. In the youngest stages, however, 

 this organ is represented only by two rudimentary buds, and it is not always possible to make sure of 

 its presence or absence ; nor can the appearance of the immature generative gland be relied on to settle 

 the sex ; in such cases the characters of the flagella and sense-tubes of the first antenna generally give a 

 clue, except in the very youngest stages. 



The measurements of the shell-length have been taken whenever possible from the inner aspect of the 

 right shell with the left shell turned back, as this is the less likely to be distorted by the dissection. 

 They -were taken with Zeiss micrometer ocular 3, in combination with objectives a.", a' (with tube at or 

 at 21 mm.), and A; the value in /jl of 20-60 divisions of the ocular micrometer, for each objective 

 and stand used, having been determined by a stage micrometer. The measurement ivas made parallel to 

 the dorsal border from the most prominent part of the anterior border, ventral to the niche for the second 

 antenna *. 



Appendages should always be drawn in the preserving fluid (formalin or alcohol) and before mounting, 

 in order to get full advantage of differences in the refractive index, when dealing with fine hairs or 

 teeth. If it is desired to mount appendages permanently for reference, Farrant's solution "ringed" 

 with gold-size may be recommended. 



No one knows better tlian the writer that the present memoir is full of unproven 

 assumptions and of arguments in a circle ; for these he offers no apology. There is no 

 harm in such assumptions so long as it is made clear to the Reader where fact ceases and 

 hypothesis begins, and so long as the evidence which has sug^e^tad the assumptions is 

 put fairly before him for his private judgment. 



It seems to me quite certain that we shall mike no a:lvauc3 ia serious oceanic 

 planktology t by the methods (or rather, lack of methods) which have hitherto prevailed. 

 No amount of hauls with vertical open nets, no nunber of handsome B/Sports on barren 

 systematic morphology, will further our grasp of this branch of Natural History. If my 

 assumptions do but stimulate some one to go to S3a in order to disprove them (criticism 

 ashore is too facile) they will have served their turn, be they right or wrong. 



In his great work on the Ostracoda of the • Valdivia ' Expeditioa, Dr. Miiller J brought 

 out the fact that the contour of the shells, the position of their glaads, and the characters 

 of the cephalic appendages (frontal organ, antenna i, antenna ii) are usually sufficient 

 for the recognition of the species. But, unfortunately, except for the shell-contour, the 

 characters which he gives apply only to sexual stages, and are useless for immature 



* This gives a real measurement of the shell, which is camparable in different species. Some previous observers 

 have measured the length from the tip of rostriitn to tip of posterior spiae, thus obtaining measurements which are 

 not expressions of the general body-length. 



t Neritio planktology with economic aims is on a different footing. 



:!: ' Wissenschaftliche Ergebnisse der deutschen Tiefsee Expedition auf dem Dampfer Valdivia,' 1893-1899, vii. 2. 

 C. W. Miiller : Ostracoda. Jena, 1906. In the following pages, where " Miiller " alone is mentionel without 

 citation, the reference is to this work. 



