222 ATTTOLYTUS PROLIFER. 



eggs. As he figures the bristle with a simple hook to the terminal piece it is possible 

 that a misinterpretation has occurred. 



Malaquin (1893) states that the formation of the sac is always subsequent to the 

 separation of the stolon, but apparently he has not seen it. The first and second setigerous 

 segments carry the eggs, and they have no swimming-bristles. The rest of the segments, 

 with the exception of a few of the last, are provided with these bristles. 



He gives a careful account 1 of the development of Autolytus from -^ mm. 

 onward. The youngest stage is devoid of bristles, shows a head with four eyes, the 

 anterior with lenses, and palpocils, a tail, and two constrictions, with cilia on the elevated 

 regions between. The pharynx is indicated. In the next stage, also achsetous, the body 

 is longer, shows constrictions, the cephalic and post-cephalic segments have cilia, the 

 pharynx abuts on an intestine, but the latter is devoid of an anus. Rudiments of the 

 lateral tentacles appear, and the proctodeum is formed. 



In the next stage the larval Autolytus is larger, the head is separated from the 

 peristomial segment, and bristles appear in the first segment, the lateral tentacles are 

 longer, and the median appears as a bud. Ciliated dorsal bands occur on the head and body. 



The pharyngeal apparatus is only completed when the young form has from twenty- 

 two to twenty-five segments. It feeds by thrusting out its proboscis and engulfing prey. 

 At the sides of the larval pharynx are glands. Moreover, Malaquin points out that at the 

 stage of eight or ten segments the larva presents two pharyngeal bulbs, the posterior 

 becoming the proventriculus. By-and-by the transformation, by disappearance of the 

 anterior enlargement, takes place, and the pharynx acquires the sinuous adult characters, 

 when there are about twenty-two segments with bristles. 



The Autolytus fallax of Malmgren (1867) does not seem to differ in any important 

 point from this species. 



In connection with this group is a bud which may be termed Autolytus A. 



Habitat. — Clinging to an osculum of Halwhondria panicea under a stone in a pool at 

 the East Rocks, St. Andrews, November 5th, 1863. 



Head rounded, small, with two large round black eyes. A comparatively short 

 median and two lateral tentacles. 



Body about half an inch long, not much diminished anteriorly, but tapered 

 posteriorly, and the segments are distinctly marked. 



The foot (Plate LXX, fig. 10) has dorsally a comparatively short and unjointed cirrus, 

 the basal region (ceratophore) apparently not being differentiated. It is tapered to a 

 blunt tip. The space between the cirrus and the setigerous region of the foot is short, 

 and is supported by some slender spines which separate from those passing to the seti- 

 gerous lobe. A tuft of very slender translucent bristles projects from this region about 

 as far as the tip of the setigerous lobe. These may be developing swimming-bristles. 

 The setigerous lobe is ovate, and has a series of slender spines in its centre. A careful 

 search furnished one or two bristles (Plate LXXIX, fig. 3) of the form shown. 



This differs from Johnston's Ioida macrophthahna in the structure of the foot, since 

 the cirrus is obscurely moniliform and twice the length of the foot, whilst there are two 



i Op. cit., pp. 392—404. 



