212 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
There are, of coarse, differences between them ; the apical plates 
and eyes seem to be absent in Awricularia, and in it the muscle-band 
from the apical plate (in Tornaria ) is not represented. The great diffi- 
culty in the comparison is the presence of two posterior pairs of entero- 
coels in Tornaria, but it is to be remembered that there are still unsolved 
problems of metamerism. The large posterior circular band of Tornaria 
seems to be a structure sui generis. 
However, the point most to be, though not generally, emphasized is 
that it is the young Tornaria and not the older larva that most closely 
resembles the Echinoderm-larva. The identity cannot be explained as 
being due to similar conditions of life in the two for. ns, for the most 
essential points of comparison relate to the internal organs. 
Mr. Morgan is of opinion that Balanoglossns has affinities not only to 
Echinoderms but also to the Chordata ; if this be so it is clear that the 
Vertebrate-phylum is a very old one, and one which it is futile to attempt 
to derive from such specialized animals as the Annelids of to-day. 
Development of Sagitta.* — M. S. Jourdain does not accept the ac- 
count of the formation of the archeuteron of Sagitta given by Kowalev- 
sky and Biitschli. The archenteron does not, he asserts, give rise to the 
coelom. He considers that what happens is this : a depression appears 
at the oral pole of the egg, and is lined by epiblast. As the depression 
becomes more and more marked it drives before it the hypoblast, which 
in time breaks through. In this way a communication is effected 
between the hypoblastic cavity and the exterior. The three archenteric 
lobes all belong to the digestive tract, and the lateral lobes gradually 
disappear. As this last event is occurring, there is a jirocess of delami- 
nation between the epiblast and hypoblast, and a mesoblastic cavity is 
thereby formed which, later on, becomes the coelom of Sagitta. With 
the growth of the embryo this becomes, posteriorly, a spacious cavity. 
On the sides of the hinder part of the intestine there appear early 
cellular growths which give rise to the male and female organs. These 
do not arise in but outside of the archenteron. Although the author 
has not been able to study in sufficient detail the development of the 
nervous system, he suspects that the type is not as far removed from 
the Vertebrate as is generally supposed ; and he thinks that Sagitta, 
Amphioxus, and the Ascidiaus form a special group which he calls 
“ Preverfebres.” 
Notops minor.f — Mr. C. Rousselet describes this new rotifer which 
he found on several occasions in Epping Forest ; it has a general resem- 
blance to N. hyptopus, but is only about a quarter of its size ; it has also 
a flask-shaped appearance, and is more compressed laterally. The 
absence of a sperm-sac shows that it is not the male of the allied species, 
as the author first thought might be the case. 
Two New Rotifers.;}: — Mr. C. Rousselet also describes Conocliilus 
unicornis and Euehlanis parva, both from Keston ; the former has the 
ventral antennae joined together within a single sheath on the surface of 
the corona ; the latter is much smaller than its congeners, has the toes 
* Comptes Rendus, cxiv. (1892) pp. 28-9. 
t Journ. Quek. Micr. Club, iv. (IS92) pp. 359-60 (2 figs.). 
J Tom. cit., pp. 367-70 (6 figs ). 
