HJALMAR BROCH. 



[REP. OF THE "MICHAEL SARS" NORTH 



The fragment from Stat. 48 comprises a cluster of 

 polyps, and under it a small part of the rachis of a young- 

 colony. Just under the terminal (primary) polyp we find 

 a pair of strictly opposite fully developed polyps (textfig. 

 2 a). The next pair are disposed at the lower side and 

 ventrally to the first; they are less than half the size of 

 the first pair, the one seated to the right of the median 

 ventral line of the rachis being the smaller of the two. 







6 o o q a 



Fig. 2. Diagrams of the polyp-clusters of Umbellula Guntheri. 

 a: The specimen from Stat. 48. b: The "Challenger"-specimen 

 (X probable seat of the rudimentary polyp), c: The specimen 

 from Stat. 47. 



In the median ventral line of the rachis, just below this 

 second pair, we see a very young bud, a polyp about 

 1 mm in length. This cluster of polyps thus belongs to 

 a decidedly younger colony than the one examined by 



KOLLIKER. 



The beautiful upper part of another colony taken 

 at Stat. 47 (pi., fig. 1) belongs to an older specimen. 

 There are in all six polyps, as in the preceding specimens, 

 the arrangement of the polyps being quite similar (text- 

 fig. 2 c). The only difference is indeed to be found in 

 the development of the polyps, which are all full grown 

 in the specimen from Stat. 47. 



Thus the three colonies of Umbellula Giliitheri repre- 

 sent three consecutive stages of development. We find 

 that the first budding from the primary polyp results in 

 two secondary polyps which are opposite and strictly 

 lateral. The next pair of secondary polyp arise ventrally 

 just beneath the first pair, and lastly an unpaired secon- 

 dary polyp buds out in the median ventral line of the 

 rachis just below the second pair. No more polyps seem 

 to develop, at any rate we do not find the slightest trace 

 of any polyp-bud in the specimen from Stat. 47, although 

 the six existing polyps are all full-grown. The tentacles 

 of the fully developed polyps are as long as the bodies 

 of the polyps, and have numerous equal-sized pinnules. 

 The measurements of the polyps give the following 

 results: — 



Stat. 47 



Terminal polyp: mm 



Length of body 11-0 



Breadth of body 3-5 



Length of tentacles 11-0 



Secondary polyps, 1st pair: 



Length of body 14-0 



Breadth of body 4-5 



Length of tentacles 16-0 



Secondary polyps, 2nd pair: 



Length of body 15-0 



Breadth of body 5-0 



Length of tentacles 17-0 



Unpaired fifth polyp: 



Length of body 15-0 



Breadth of body 4-5 



Length of tentacles 17-0 



Length of the swollen upper part 



of the rachis 26-0 



Stat. 48 

 mm 

 9-0 

 3-5 

 9.0 



14-0 



3-5 



13-0 



5-0 1 ) 

 2-0 1 ) 

 6-0 1 ) 



1-0 

 0-5 

 not developed 



23-0 



The zooids are pretty numerous on the swollen upper 

 part of the rachis, filling out every interspace between the 

 bases of the polyps except for one narrow streak in the 

 median dorsal line. This bare streak is situated along 

 the axis, which is visible in the broad polypless, dorsal 

 flattening of the rachis. 



The upper zooids of the rachis show no trace of 

 tentacles. Just beneath the swollen part of the rachis, 

 where the stem is quadrangular, the zooids are extremely 

 small and flattened. Zooids are found only here and there 

 on the lateral side of the thin stem. After a very careful 

 examination of a second fragment from Stat. 47, consisting 

 of the lower part of a colony, we also found them where 

 the lower part of the stem begins to swell. 



The axis is quadrangular, with concave sides and 

 prominent rounded edges; it is a little thicker in the stalk 

 than in the rachis. 



The sarcosoma of the stem and the walls of the polyps, 

 as well as the tentacles, are studded with spicules. No 

 formation of calyx could be found, because of the studding 

 of spicules, as described by Kolliker 2 ) in the "Challenger" 

 specimen. 



The different forms of spicules are very characteristic 

 (textfig. 3). Those of the tentacles are smooth and tripen- 

 nate with square ends which often seem to be composed 

 of small crystals; these spicules attain a length of 0-6 mm. 



') Measured on the larger polyp of the pair. 

 2 ) Kolliker 1. c. 1880, p. 19. 



