the Development o/Phyllodoce maculata. 105 



sent the animal just after it leaves the gelatinous investment 

 and assumes a more elongated form. Dr. Max Miiller*, in 

 his description of Sacconereis helgolandica^ refers in a footnote 

 to a young PhyUodoce from Heligoland, which, however, had 

 reached a recognizable condition, being furnished with twenty- 

 six segments, each of which had the characteristic bristles and 

 other appendages of the feet. Mr. Alex. Agassizf lately added 

 still further to our infonnation on the subject by his remarks 

 on the development of PhyUodoce maculata^ (Ersted, his de- 

 scription commencing at an earlier period than that referred to 

 by Dr. Max Miiller in his form, — viz. on the appearance of the 

 tentacles, but before the advent of the bristles. 



On the 15th of May various examples of the adult Annelids, 

 loaded with ova and spermatozoa, were received from St. An- 

 drew's ; and each very soon deposited the green spawn on the 

 sides of the vessel in a somewhat bulky, transparent, gelatinous 

 mass, and discharged at the same time a copious cloud of 

 spermatozoa. On deposition, the ova (PL VI. fig. 1) are of a 

 fine grass-green colour, minutely granular, with a clear spot 

 and a single thin investment. The bodies of the spermatozoa 

 are shaped somewhat like a nine-pin, with a small rounded 

 head, towards which the body tapers anteriorly, and with a 

 blunt posterior extremity which gives origin to the long fila- 

 ment or tail (fig. 2). 



To take for instance the ova deposited about 7 A.M. on the 

 18th, it is found at 9 A.M. that the yelk is separated into two 

 masses (fig. 3), and moreover that, when moderate pressure is 

 maintained for a time, a further division into fom* occurs 

 (fig. 4), and in a few hours after all are found in the mulberry- 

 stage. Next day the exterior of the ovum becomes distinctly 

 ciliated, though the action is feeble and the organs short 

 (fig. 5). There is no extrusion out of an egg-capsule in this 

 case, the thin investment of the yelk being the only covering. 

 The body is nearly round, and at first sight seems to be co- 

 vered with cilia ; but a brief examination in various positions 

 shows that these organs are arranged thus : — A belt of cilia 

 entirely surrounds the body, a long brush springs from a point 

 a little behind the anterior border, and a shorter tuft of scarcely 

 projecting cilia marks the large aperture in the posterior region. 

 The cilia of the ring gradually increase in length and power ; 

 so that swarms of the young leave the gelatinous mass and con- 

 gregate on the bottom of the vessel like a green powder. On the 

 third day they have become much more lively, and two eyes also 

 appear (fig. 6). When, in this stage, the animal is viewed from 



* Archiv fiir Anat. 1855, p. 17. 



t Ann. Nat. Hist. ser. 3. vol. xix. p. 249, 1867. 



