18 
A smaller part of the individuals have been preserved in for- 
malin, which gives a very good result. There is little or no con- 
traction of the muscles, so that the animals keep very nearly their 
original shape and size; they are well hardened and not apt to 
break, and though the specimens so treated do not possess the 
complete transparency of the living animals, the inner organs are 
fairly distinctly visible. In order to study the state of maturity of 
the sexual organs it is, however, often necessary to treat the spec- 
imens with xylol; as to the species, dealt with in the present 
paper, such clearing with xylol has been necessary particularly in 
the cases of Sagitta elegans, while S. maxima and Eukrohnia 
hamata retain their transparency fairly well after the preservation. 
The vivid colours of the reproductive organs of E. hamata when ma- 
ture are, fairly well retained in formalin. — An absolute neces- 
sity for a good result of the preservation is, that the jar does 
not contain too many specimens. Fowler who warmly recommends 
formalin for preservation of chaetognaths will say, that the best 
result is gained, when every single individual is preserved in ER 
jar by itself. It is true that a number of specimens being killed 
within the same jar will attack and hurt eachother in their agonies 
of death, and if a specimen has cut its hooks into the body of 
another, it is impossible to separate them without destroying one 
or both of them. — Chaetognaths preserved in formalin may with- 
out damage be transferred into 70 alcohol, if it be done by 
degrees. 
The material of chaetognaths brought home by the "Tjalfe" 
expedition is very large. Most of the Samples contained hundreds 
of specimens, some even several thousands. The bulk of the mat- 
erial is constituted by the three species: Eukrohnia hamata MO- 
bius, Sagitta maxima Conant, and Sagitta elegans Verrill. More- 
Over some individuals of S. planktonis Steinhaus were found. Some 
specimens of Eukrohnia fowleri Ritter-Zåhony were captured by 
deep-water hauls in the Davis Strait; they were preserved separately, 
because they were conspicuous at once owing to their red colour. 
The distinction of the four other species was not difficult. I have 
been able to separate them by means of the naked eye or a pre- 
paration lens. All Young specimens, however, have been examined 
under the microscope. 
