Miscellaneous, 495 



vessel, which is turned towards the interior of the ovary, and at the 

 expense of the epithelial cells forming that wall, to which, at first, 

 they remain attached by a peduncle ; they afterwards become de- 

 tached, descend along the lobe, and then arrive in the oviducts ; 

 thus they never fall into the general cavity. The sexual lobes are 

 of very unequal length in the same animal, and unequally developed 

 in different individuals according to the age ; in Sternaspides of 

 large size, especially in the males, they present short secondary lobes 

 along the principal branches of the sexual vessel. 



In front of the oviducts and involved in the folds of the oeso- 

 phagus, there exist two voluminous segmental organs (" four- 

 homed organs " of Miiller), of a brown colour, with dehcate walls, 

 irregularly lobcd, and each furnished with an excretory canal, 

 which becomes much narrowed towards the integuments, and opens 

 outwards by an extremelj' small pore. The two symmetrical pores 

 are placed in front of the genital appendages. I have not yet succeeded 

 in detecting vibratile funnels in connexion with these organs ; they 

 present an internal epithelium and an external peritoneal layer, 

 and between the two a rich network of often capillary blood- 

 sinuses. 



Hitherto I have only been able to observe the first phases of the 

 embryogeny as the result of artificial fecundations. The ova are 

 about 0-15 millim. in diameter ; within their chorion, which usually 

 retains a trace of the pedicle, they present a granular vitelline mass 

 with an eccentric nucleus and a nucleolus ; this nucleus disappears 

 in the mature ova. The spermatozoids are from 0*085 to O'lO millim. 

 in length ; the head is elongated, and occupies about one sixth of 

 the entire length. The segmentation is complete; it commences 

 about five hours after fecundation. Even the first two spheres are 

 unequal ; and the difference becomes rapidly more accentuated be- 

 tween the small hyaline evolutive cells and the large, dark, granular 

 nutritive cells ; the former quickly envelop the latter, and thus form 

 a planula by epibolism. In four-and-twenty hours I found in the 

 glasses pelagic larvae composed of an ectoderm with small elements, 

 and an endoderm formed of a few large brownish spheres ; they 

 appear to be destitute of both mouth and anus. These larvce are 

 covered with vibratile cilia, except in the posterior region ; at their 

 cephalic pole they bear a plume of longer cilia. But the pelagic life 

 hardly lasts longer than from thirty-six to forty hours; the larvae 

 fall to the bottom of the water, lose their cilia, become elongated, 

 and assume a vermiform appearance and movements. The evolu- 

 tion is afterwards very slow in the glasses ; at the end of a month 

 the larvae, although considerably more elongated, present a digestive 

 tube formed of large cells and destitute of mouth and anus ; its 

 cavity is filled with a liquid which bears numerous granules, and 

 which the movements of the body cause to travel from before back- 

 ward or vice versa; in the posterior region and on the dorsal (?) surface 

 we may distinguish a small ectodermal appendage bent into a hook, 

 which may be the first rudiment of the brauchiae. — Comptes Rendus, 

 May 2, 1881, p. 1066. 



