Plate I. 



The figures represent different specimens of Tjalfiella tristoma Mrtsn. 



Fig. i. Photograph of two specimens in their natural position on the stalk of Umbellula Lindahli; 

 the upper one in side view, the lower one somewhat obliquely from above. The white corpus- 

 cles are the genital organs. The specimens were still in formaline when photographed. Natural 

 size. 



2. A young specimen, without embryos. Side view. 8 / t . 



3. A slightly older specimen, with one embryo. The specimen was cleared in xylol, the stomo- 

 daeal folds thus becoming visible through the body wall. The two median genital organs are 

 distinctly seen to consist each of two parts, viz. the median part being the ovary, the outer 

 part the testis. The branching canal system is perhaps not correctly shown in all the outer 

 branchings, these being not quite discernible in the cleared-up specimen. Side view. 8 / r . 



4. Specimen showing the right half in regeneration. No embryos. Side view. 9/j. 



5. Young specimen, without embryos. The small size of the outer left genital organ perhaps 

 indicates, that this part has been regenerated. (The lower corner to the left slightly restored). 

 Side view. B -s/ t . 



6. Fully developed specimen, seen from above. ?/j. (Same specimen as Fig. 9). 



7. Specimen having lost the right "chimney" with the tentacle and the outer pair of genital 



organs; the regeneration has scarcely begun, but the edges of the rupture have closed. 

 Side view. 8iS /i- 

 8. Specimen in regeneration. Side view. 8 / t . 



9. Fully developed specimen, with numerous embryos. Same specimen as Fig. 6. Side view. 7/ t . 



Some pigment is seen within the embryos, having become distinct through the clearing up 

 of the specimen in xylol. The branching canal system, on the other hand, became indistinct 

 through that process and is therefore represented in a somewhat diagrammatic way. 



