228 DK. a. H, FOWLER — BISCAYAN PLANKTON : 



the case *. For example, Miiller notes under many species that the Antarctic specimens 

 were larger on the whole than those from the tropical and temperate regions traversed 

 by the ' Valdivia.' Again, not all observers measure the same " length " : Dr. Miiller 

 seems to have included the rostrum, and a spine when present. 



Eor diagnostic characters I have followed Miiller's admirable selection as far as 

 possible, except in the case of the shell-sculpture. In formalin specimens of most of the 

 species whicli I have seen, the sculpture is often so difBcult to make out (as, indeed, 

 Dr. Miiller himself admits), that it can only be regarded as a secondary diagnostic 

 character at best. Of two specimens of the same length and the same species from the 

 same haul, it may be conspicuous in the one, nearly invisible in the other. 



As regards the various glands, for the diagnostic value of which we are indebted to 

 Miiller, a little caution is necessary. They were by no means always so obvious in my 

 formalin material as they appear to have been in the ' Valdivia ' collections. Some 

 experiments in staining seemed to show that the obviousness of the glands when 

 unstained varied very much, and presumably depended upon their physiological 

 condition (secreting or discharged) at the moment of death. 



If it is desired to stain formalin specimens for the glands, the following method will be found useful : — 

 To a (7 per cent.) store solution of formalin add 5 per cent, of Delafield's hijematoxylin ; the mixture 

 should be made fresh daily, and filtered. After immersion in this for about twenty minutes, the 

 apertures of the gland-cells will be found deeply stained, the cell- walls slightly stained ; the asymmetrical 

 glands assume a brownish-yellow tint. 



As with other smaller members of the macroplanlcton (excepting Ctenophord), formalin is the best 

 reagent both for killing and storing. Mercury bichloride is detestable, rendering the tissues opaque and 

 unyielding, and covering the specimens with a dust of apparently insoluble mercuric compounds. 

 Alcohol leaves the specimens clean, but equally opaque and resistent. Picric acid did not seem to have 

 any special value. 



HALOCYPRID^. 



The species of Conchcecia in this memoir have been arranged in alphabetical order for 

 convenience of reference. The following table shows their distribution according to the 

 groups recognized by Dr. Miiller : — 



Group of Species. 



spinifera spinifera. 



incrmis, 



elegans elegans. 



procera procera=deeipiens. 



brachyaskos. 



* In this connection Conchcecia would form an interesting test-case of the suggestion which has been put 

 forward, thai polar, sub-polar, and deep-water forms — that is, cold-water forms — owing to a less rapid metabolism, 

 live longer, become sexual later, and grow larger, than forms of the same species in tropical waters. 



