1885.] Zoology. 1109 
Balanoglossus presents resemblances, though with some differ- 
ence, to Amphioxus in the following points: Origin and persis- 
tence of the notochord and its relation to the alimentary canal, 
position of the biood-vessels of the gills and the form of the gill 
bars, position and mode of origin of the central nervous system, 
origin of the mesoblast and body cavity, the atrial fold' and the 
duct from body cavity into the atrium—similar to the excretory 
tube of Amphioxus. 
The complete discussion of the affinities of Balanoglossus is 
reserved for a future paper, but Bateson proposes to associate it 
as follows : 
Hemichorda as Enteropneusta 
Urochorda = Ascidians 
Cephalochorda oa Amphioxus 
Vertebrata, 
— Henry Leslie Osborn. 
THE REPRODUCTION OF THE Common MussEL.—Professor W: 
C. M'Intosh describes the reproduction of the mussel (Mytilus 
edulis), The sexes are distinct in the adult form, but in the unde- 
veloped condition the structure of the organs seems to be similar 
in both sexes, The shape of the valves gives no reliable distinc- 
tion. The reproductive elements are developed in the mantle; 
the male presents in January, in the thickened generative region 
of the mantle, large pale round sperm-sacs filled with minute . 
Spermatozoa, which have minute ovoid bodies with finely fila- 
mentous tails. They are lively and tenacious of life. Twenty- 
four hours of exposure, however, seems to be fatal to them. The 
emales have the same region of their mantle crowded with a pro- 
digious number of minute ova. Throughout February the devel- 
opment increases, and the whole surface of the mantle becomes 
Speckled in both sexes with the reproductive elements. After 
full maturity is attained, as in April, the orange mantle is richly 
marked in an arborescent manner by racemose sperm-sacs and 
ducts, especially towards the margin. In the females this is not 
So evident, the ova being grouped in masses and densely packed. 
From this time the activity of the spermatozoa and the number 
of the ova diminish, till in July neither ova nor spermatozoa can 
be distinguished microscopically.—/ournal of the Royal Micro- 
Scopical Society, June, 1885. 
MANNER IN WHICH THE LAMELLIBRANCHS ATTACH THEMSELVES 
To Foretcn Osjects—Dr. J. T. Cattie describes the means by 
which the common mussel attaches itself to foreign objects. 
When the foot commences to grope about, it may become two 
or three times as long as the body of the animal without finding 
any object within its vicinity ; it then moves about till it finds some 
Point of support, when this is effected there appears from the 
transverse cleft which terminates the ventral groove a whitish sub- 
