254 MR. F. D. DYSTER ON PHORONIS HIPPOCREPIA. 
under the integument, and is not ciliated. The ova lie in its upper and visible portion 
for some hours, vibrating backwards and forwards under the influence of the wave of 
blood in the hæmal vessel. They are driven slowly upwards, till they arrive between 
the two ducts which appear as ridges under the rami of the lophophore. The oviduct 
here seems to contract in its dimensions; and the ova assume a cylindrical form. They 
pause here for about half an hour; but at length the upper end of the cylinder dips sud- 
denly downwards, passes into the hollow ridge, and then mounting through it, is dis- 
charged in a spherical form into the space between the inner tentacles, to which the 
ova adhere by a glutinous exudation. They are voided alternately through each ridge, and 
form a compact white mass, separable only with considerable difficulty, on each side of 
the space in the concavity of the horseshoe, shadowed over by the interlacing extre- 
mities of the inner tentacles. They vary in number from 10 to 80. When first extruded, 
they are granular with a clear margin, and show the usual germinal spot on pressure. 
In a few hours, cilia are developed all over the surface; and two depressions appear on the 
circumference, indicating a circular groove. This groove rapidly deepens; and within 
twenty-four hours the young exhibit distinctly a cephalic and an abdominal segment; ante- - 
riorly the line of separation deepens; and the abdominal portion becomes concave on the 
upper surface, alternately receding from and embracing the convex surface of the cephalie 
portion which lies above it. The cilia increase in length and power; and very soon, in 
certain positions, the alimentary canal becomes distinguishable. The cephalic segment 
divides into three lobes, of which the lateral are the longest and anterior, the central 
highest and posterior. The larva has now great power of locomotion, and quits the 
parent-nest when about forty-eight hours old. 
The principal point of interest in the Phoronis is the indubitable presence of blood- 
corpuscles in proper closed vessels of the circulatory system. Von Siebold* is obscure and 
brief on this subject, and simply says—“ the blood of the Annelids . . . is composed of å 
liquid containing globules... which are always colourless and of a spherical form.” 
Milne-Edwards+ says that, in the Vertebrata, “la couleur rouge du sang est due aux glo- 
bules que ce liquide charrie; chez les Vers å sang rouge, c’est en dissolution dans le liquide 
lui-méme, que se trouve la matière colorante. .. . Les globules ne jouent dans cette colora- 
tion aucun róle essentiel, et d'ordinaire ces corpuscules paraissent méme manquer compléte- 
ment dans ce liquide. . . . M. de Quatrefages a été niéme conduit à penser que dans l'im- 
mense majorité des cas, le sang rouge des Annélides est complétement privé des globules quel- 
conques. Il n'a rencontré qu'une exception à cette regle, et elle lui a été fournie par une 
espèce de Glycère des côtes de la Manche, chez laquelle il a trouvé des globules rouges et de 
forme discoïde, nageant dans un liquide incolore. Mais M. Williams t, qui a publié récem- 
ment une série nombreuse d'observations sur le fluide nourricier des animaux invertébrés, — 
affirme que cette exception n'existe pas; que les globules rouges décrits par M.de 
Quatrefages se trouvent dans le liquide de la cavité générale du corps, et non dans les 
vaisseaux sanguins, et que dans aucun Annélide le sang proprement dit (ou sang coloré) 
P å 
Von Siebold, Comp. Anatomy, translated by Burnett, vol. i. p. 168. 
+ Leçons sur la Physiologie, tome i. pp- 106-108 et note. 
+ On the Blood proper and Chylaqueous Fluid of Invertebrate Animals.— Philosophical Transactions, 1852, p. 63°: 
