496 TRANSACTIONS OF SECTION D. 
Delage’s method consists in treating the unfertilised eggs with tannic acid and 
ammonia in a mixture of sea-water and cane-sugar. The proportions we found 
most favourable for /. esculenius at Plymouth were 10 c.c. sea-water + 40 c.c. 
cane-sugar solution (strength, 388 grms. to a litre) + 1-4 c.c. M/60 tannic acid : 
the untertilised eggs were placed in this for six minutes, and then 1°5 c.c. M/10 
ammoma were added for one hour. We have obtained 8U per cent. blastule by 
this method, but they are not healthy and die off rapidly during the first week. 
‘’nere 1s no membrane formation by Velages method. 
‘he method which we have found most successful consisted in treating the 
unfertilisea eggs first with butyric acid to cause membrane formation as in 
Loeb’s method, and then by Delage’s method as described above. In this way 
we have obtained as many as 90 per cent. blastule. The larve are vigorous and 
grow for the first three weeks as rapidly as larve from fertilised eggs, 
6. A Sessile Clenophore, Tjalfiella tristoma (Mrtsn.), and its Bearing 
on Phylogeny. By Dr. Tn. Mortensen. 
On an expedition to West Greenland in 1908, Mr. Ad. 8. Jensen found in the 
deep Umanak fjord a curious animal, attached to the stems of Umbellula 
Lindahlii. It proved to be a Ctenophore of quite unusual interest, being the 
first sessile Ctenophore known; moreover, it was found to be viviparous, a con- 
dition likewise hitherto unknown among Ctenophores.* 
The shape of the animal is quite unlike anything else among Ctenophores. 
The body is compressed, elongated in the transverse plane, and has at each end 
a tower- or chimney-like elevation with an opening at the top. This shape is 
the natural consequence of the fact that the animal attaches itself with its mouth, 
thus making it impossible for the mouth to perform its duties as such. A func- 
tional moutb-opening being, however, a necessity, the animal helps itself in this 
way, that the mouth-edges are turned upwards and raised on the said little 
towers. The animal thus gets in reality three mouth-openings, the original one 
remaining open though out of function. The costz have totally disappeared. 
The apical organ is rudimentary, being—as a static organ—of no use in a sessile 
organism, ‘I'he tentacles are simple. There are no meridional canals; on the 
otner hand, there is a branching canal-system as in Cwloplana and Utenoplana. 
Four pairs of prominent knobs, situated along the upper side of the body, repre- 
sent the genital organs, the structure and arrangement oi which are in perfect 
accordance with that typical in Ctenophores. ‘The eggs are developed in brood- 
chambers on the sides of the body. ‘lhe young, which is a true Cydippid, with 
well-developed costa, has a pair of oral transversal lobes, recalling the lobes of 
the Lobatw. It swims about for a very short time, then attaches itself with the 
mouth (more precisely, with the inside of the spread-out oral lobes), looses its 
coste, and at once begins to form the chimneys with the secondary mouth- 
openings. 
Tjalfiella is doubtless nearest related to Caloplana and, especially, Cteno- 
plana. ‘The several important anatomical differences apparently existing between 
Ljalfiella and Ctenoplana, the latter being stated to have unisexual genital 
organs with separate ducts, a peculiar gastric gland, chloragogenous cells, &c., 
appear to rest altogether on misapprehension. 
In regard to phylogeny great importance attaches to 7'jalfiella. The theory 
of Selenka and Lang, according to which the Polyclads derive from the Cteno- 
phores, has been much criticised in recent times, especially by Willey, who 
maintains that Ctenophores and Polyclads have developed along different lines 
from forms like Caloplana and Ctenoplana, which are thus regarded as the 
most primitive of all Ctenophores. The anatomy and development of 7'jalfella 
are, however, decidedly in favour of the theory of Selenka-Lang; it can no 
longer be doubted that the Platyctenida are really the most specialised of all 
Ctenophores, showing the way along which the Polyclads developed from the 
+ A preliminary description was published in Vidensk, Medd. Naturh. Foren. 
K¢benhavn, 1910; the full report has been published in May this year (1912) ia 
the ‘Danish Jngolf Expedition,’ vol. y., 2, ‘ Ctenophora.’ 
