20 
elopment the testes have a gritty appearance. Within the same 
polyblast all the spermatocytes follow each other almost exactly as 
to their further development, and so they all at the same time are 
divided into spermatides which quickly develope into complete sperm- 
atozoa. When this ripening process has commenced, the groups 
of spermatozoa are distinctly visible among the polyblasts containing 
spermatocytes. The formation of spermatozoa is commenced in the 
foremost part of the testes, but a number of ripe polyblasts may 
be found in the hind part, while groups of spermatocytes are still 
present in the front part. As thus the ripening of the testes takes 
place by degrees it is impossible to state a definit limit between 
ripe and unripe male organs; practically spoken I have called them 
fripe", when ripe polyblasts are found through the whole length of 
the testes. 
In the young. ovaries all of the eggs are nearly the same size 
and very small. When the adult age is approaching, the ovaries 
grow in length, sometimes they also become broader, mainly owing 
to the formation of more eggs, not because the eggs increase in 
size. Åt a certain stage one or more eggs increase very much in 
size, become mature, and break their way into the temporary ovi- 
duct (described mainly by Stevens (1910), Buchner (1910) 
and Elpatiewsky (1910)). More eggs follow, in an irregular 
manner, and at last the oviduct is filled by large mature eggs. In 
the following pages I have called the ovaries mature, when the 
oviducts are filled by mature eggs. 
The distribution and occurrence of the five species here men- 
tioned are somewhat different. Sagitta planktonis and Eukrohnia 
fowleri are wholly oceanic species occuring in the deep parts of 
the oceåans; they seem to be fairly scarce in these northern lati- 
tudes, and they are found in the atlantic water exclusively. Sagitta 
maxima and Eukrohnia hamata occur in large quantities in the 
cold seas, particularly in the deeper strata, but they may also 
be found in the upper layers, even close to the surface, though 
always in small numbers; as a rule they keep themselves rather 
far from the coast. Sagitta elegans, on the other hand, is a coastal 
water species, though in the waters at Greenland it seems to pre- 
fer the deep parts of the coastal area; the var. arctica has a well 
marked arctic distribution. 
