ON THE MARINE BIQLOGICAL LABORATORY, PLYMOUTH, 4.37 
Investigations made at the Marine Biological Laboratory, Plymouth.— 
Report of the Committee, consisting of Mr. G. A. BouRNE (Chair- 
man), Professor E. Ray Lankester (Secretary), Professor 8. H. 
Vines, Mr. A. Sep@wick, Professor W. F. R. We.pon, and Mr. 
W. GARSTANG. 
PAGE 
The Embryology of the Polyzoa. By T.H. TAYLOR. F ‘ : E . 437 
The Rearing of Larve of Echinide, By Professor E. W, MACBRIDE - . 438 
The Embryology of the Polyzoa. By 'T. H. Taytor. 
BowERBANKIA was found at the beginning of August to be breeding. 
Stones and shells with healthy colonies were dredged from the sound and 
placed in vessels of sea-water well supplied with suitable algz, and larve 
were spawned in abundance. The larva is found in the parent polypide 
in the tentacle-sheath by the eversion of which it is passed to the exterior. 
Spawning generally takes place in the morning, only an occasional larva 
appearing after midday. 
The larve are strongly influenced by light, and it is easy to cause 
them to migrate from side to side of the aquarium by altering the illu- 
mination. In order to test their response a beaker was wrapped round 
with black paper on one side of which a window was cut. On introducing 
the larvee, they quickly appeared at the window, and remained there 
swimming about for some time. Eventually they disappeared, and were 
found to have settled on the floor of the vessel. 
The free swimming period is very short. Of a batch spawned in the 
morning almost all have fixed by the early afternoon, and it is rare to 
find any left in the evening. The study of the free larva is greatly 
facilitated by its capacity for intra-vitam staining: toluidin blue was 
used for this purpose. After fixation the larva rapidly passes through 
its metamorphosis, and becomes a hemispherical cystide covered by a 
delicate cuticle, and containing the degenerated larval tissues. From one 
side a blunt process grows out as a stolon over the surface of the sub- 
stratum, and is cut off by a septum from the cystide, which gradually 
develops into the primary polypide. 
As the attachment of the cystide is very close, and cannot be loosened 
without injury, advantage was'taken of the response to light in the larva 
to secure its fixation on a manageable substratum. Celloidin films were 
used according to the method adopted by Pronho for polyzoan and by 
Vosmaer for sponge larve. There is a great advantage in working with 
larvee fixed on films, as there is no risk of losing them while they are 
being carried through the various reagents ; and celloidin is very suitable, 
as it is quite transparent, and tears into convenient strips. After the 
larve had fixed the films were transferred to an aquarium and kept till 
required. In this way a series of stages was obtained. Flemming and a 
mixture of acetic and corrosive were used as fixatives. 
I have to express my sincere thanks to the Committee of the British 
Association for their permission to occupy their table at the Plymouth 
Laboratory, and also to Mr. E. J. Allen, the Director, for his kind interest 
and many helpful suggestions. 
