1899] EPITO ROUS FORMS OF ANNELIDS 379 



furnished with long swimming bristles, like a pelagic Autolytus. These 

 take the place of the bristles described in the first form. Some of the 

 spatulate forms remain, however, posteriorly. The perivisceral cavity 

 is frequented by the gregarine Gonospora longissima. This form, there- 

 fore, is modified for a more or less pelagic existence. 



The authors give an elaborate description, with tables, of the 

 setigerous apparatus and the various modifications it undergoes in the 

 several forms (simple and spatulate). They also append a table of 

 the bristles in the developing forms — from those having one setigerous 

 segment to those with eighteen. 



The eggs in the first form (A) are bluish-green, and are set free, as 

 usual, from the ovigerous masses into the body-cavity, from May to the 

 end of summer. Moreover, the authors found trochospheres and 

 embryos of several segments in the coelomic cavity — showing that the 

 form is viviparous. When the embryos are large, their number is few 

 in contrast with the eggs, so they suppose that the larvae are extruded 

 by the segmental organs in successive sets. The authors think that 

 the shedding of the reproductive elements is the end of the individual. 

 They also describe, however, brownish masses about the size of these 

 larvae, which may be degenerating forms in process of removal by 

 phagocytes. Further, the authors consider the form is parthenogenetic, 

 for they have found no trace of sperms or of spermatogenesis. Out of 

 several thousands they observed not a single male. The possibility of 

 impregnation from without is not, however, seriously discussed by 

 the authors. They challenge the opinion of Monticelli, who states that 

 this form is a hermaphrodite protandrous one. 



In the second form (C) only a single female approaching maturity 

 was observed in April. The ova are smaller than in A and B, and pass 

 out by the segmental organs probably into mucus, unless this form also 

 is parthenogenetic. 



In the third form (B) the sexes were found more evenly balanced, 

 and maturity appeared to be in August. In these the eggs were 

 brownish, and larger than in either of the foregoing. In their pelagic 

 condition the ova and sperms are discharged, and development takes 

 place in the sea, the young forms only returning to the alga when their 

 pelagic life ceases. 



So minutely did the authors carry out their investigations that they 

 followed the developing forms of the three series in regard to the modi- 

 fication of their bristles and other parts. Thus, in form A, two eyes 

 appeared in the earlier stages, viz. at 15 segments, and disappeared 

 about the stage with 30 segments. The modifications of the short 

 serrated bristles into the spatulate serrated and the spatulate, the 

 appearance of the palps and branchiae, and the growth of the thoracic 

 and the two parts of the abdominal region of the body are also described 

 as far as the truly adult condition. 



Of the second form (C), very few of which, however, were procured, 



