
1891.] Embryology. g21 
it is seen that of the two furrows mentioned but one is a true cleavage 
furrow, and it divides the egg into a larger and asmaller moiety. One 
_ of these protuberances is cut off to form a macromere equal in size 
with the two smaller ones; the other protuberance is a part of the 
larger macromere, and again fuses with it. There have thus been formed 
by two vertical furrows, comparable to the first and second cleavage 
furrows of Crepidula, three small and one large macromere.”’ 
A preliminary note is published by T. H. Morgan on the larva of 
Balanoglossus,—Tornaria. Reasons are given for regarding the common 
Tornaria of the New England coast as belonging to a different species 
from the B. kovalevshti of the same coast, so that the parent form is not 
at present known in connection withthe larva. A description is given 
_of the formation of the different organs as they appear in the life of 
the larva; for instance, the so-called heart (proboscis vesicle or 
gland) probably originates from a very few mesenchyme cells; the first 
pair of paired cavities arise as proliferations from two points in the 
walls of the stomach, and the second (last) pair of paired cavities 
arise as solid folds from the posterior division of the digestive tract 
(endodermal); the nerve-chord is formed by the collar rolling over 
the invaginating plate of ectoderm from the two sides, exactly as in 
Amphioxus. ‘‘ The similarities of Tornaria to the Echinoderm larva 
are very numerous, and I cannot believe are due to superficial resem- 
blances. If this be true, the antiquity of the larva must be very great, 
though not necessarily ancestral. The relationship of Balanoglossus to 
the vertebrates seems more than probable, as Bateson has pointed out.” 
The two papers by Prof. F. H. Herrick on the American lobster have 
been already reviewed in the July number of the NATURALIST. 
Prof. Brooks has a short note on some interesting structures in 
the early stages of echinoderm larve. ‘‘Several observers have 
recorded the occurrence of a right water pore and pore canal, as well as 
those which occur normally on the æft side, . . . but the former have 
heretofore been regarded as monstrosities, Inthe summer of 1889 I 
collected with a tow net, in the open waters of Wood’s Holl, great 
numbers of normal, vigorous starfish larvee ; and upon studying their 
structure by serial sections I found that the water system is at first 
bilaterally symmetrical in every particular, although the right water pore 
and pore canal degenerate and disappear very early in the life of 
the larvæ, so that the older larve exhibit no traces of those structures, 
. The phenomenon in question has a direct bearing upon the 
significance of the ciliated, bilateral swimming larva of Echinoderms, 



