22 THÉEL, NORTHERN AND ARCTIC INVERTEBRATES. I. SIPUNCULIDS. 
Phascolosoma, which I have named Ph. Sabellarie and Ph. improvisum. During the 
course of several years I have had opportunities of examining numbers of them at 
the Swedish Marine Biological Station at Kristineberg, and always with the same 
results. With a passing reference to the special information given further on, I prefer 
here only to remind my readers of the followimg facts: 
1. That the two forms in large quamtities pass their lives elose together, side 
by side, at a trifling depth, hidden among the sandy tubes of Sabellaria spinulosa, 
and living on dead shells of Cyprina islandica and other bivalves. 
2. That the smooth form (Ph. Sabellarie), devoid of papille and hooks, always 
has the body-cavity filled up with ova during the summer and autumn, and that these 
are often of very considerable size. 
3. That the rough form (Ph. improvisum), provided with papille and hooks, 
is always devoid of ova. However, it must be admitted that I never found in them 
mature spermatozoa! 
4. That in all other respects the resemblance between them is striking, and 
finally 
5. That the smooth form in a very few cases is furnished w mn some scattered 
hooks, thus presenting a transition-stage. 
From this, one must not infer that a dimorphism here really exists, but a 
possibility of it is not totally exeluded. Further investigations may show how the 
matter really stands. 
Parasites. 
In 1903 AUGENER"' described some parasites from the perivisceral cavity of 
Sipunculids, viz. developmental stages of Sporozoa, a new Nematod and a new peculiar 
parasitie Copepod. From my own investigations I can report that a form of Sporozoa 
is very often met with in the body-cavity of Phascolosoma Sabellarie. There is also 
to be found, though very sparsely, a minute parasitie Copepod, which bears a very 
marked resemblance to Siphonobius gephyreicola, described and figured by AUGENER 
as found in the hbody-cavity of a tropical Aspidosiphon. However, it certainly repre- 
sents a new species, possibly also a new genus. Posteriorly it was provided with two 
rather long egg-strings. 
The intestinal canal of Phascolosoma Sabellarie commonly harbours a number 
of rather large worm-like organisms with lively, swinging movements, like those of a 
Nematoid worm. They are unicellular, elongate and fusiftorm, with a distinet oval 
nucleus and apparently devoid of cecilia. There are probably two forms, one more 
inert and with one end more rounded, while the other is very active, is tapered 
tosvards each extremity and has longitudinal ridges. 
" Archiv för Naturgeschichte. 69 Jahrgang. I, B. 3 heft, Berlin 1903. 
