On the Development of the Pycnogons. 195 



stems of Bugula plumosa, a littoral Zoophyte on the Durham 

 coast — although various Zoophytes from deep water have been 

 subjected to the most careful scrutiny. Several curious little 

 animals were found on this Zoophyte a few years ago, at a 

 time when the early stages of the Pycnogons were unknown 

 to the writer ; they proved a complete puzzle until earlier and 

 later stages were found, when an insight into their probable 

 character was gained, and extended observations on the de- 

 velopment of these animals clearly established the early life of 

 Nymphon. 



A reference to the plate accompanying this will enable 

 the reader to understand the further changes which take 

 place. It will be observed that the posterior portion of the 

 body is obtusely rounded, this gradually changes, until at 

 last a slight notch appears on each side, which becoming more 

 decided presents the appearance of three narrow lobes. These 

 separate from each other, those on each side gradually elon- 

 gating and developing into legs; whilst the centre one, 

 increasing in width, pushes out the newly formed limbs in a 

 lateral direction. The joints are then visible, at first close to 

 each other; but by degrees they increase in length, after 

 which the claws on the terminal joint appear. The hairs are 

 also produced, and the little animal presents a most grotesque 

 appearance (see Fig. 2). The posterior portion, meanwhile, 

 continues to elongate, and going -through the process just 

 described, a second pair of legs is the result ; again it repeats 

 the operation, when a third pair is produced. The young 

 animal now closely resembles a Pycnogon, excepting the pre- 

 sence of the anterior rudimentary limbs and the large spine 

 on each foot-jaw ; if it were rid of these, it might readily pass 

 for a young Pycnogon about to produce its fourth and last 

 pair of legs. We accordingly find that these rudimentary 

 limbs, having served the requirements of the larval stage, are 

 now no longer needed, and are readily got rid of by a moult, 

 which takes place at this stage, the fourth pair of legs being 

 usually produced at the same time. Having neither palpi 

 nor false feet it is of course far from perfect, and might be 

 either a Nymphon, a Pallene, or a Phoxichilidium, for what we 

 could tell. These important organs are afterwards produced, 

 the palpi being the first of the two to appear. Near the base 

 of the foot-jaws a wart appears, which gradually elongates 

 and developes into these well-known and characteristic parts. 

 The false feet are produced in a similar manner, from a wart 

 growing near the origin of the first pair of legs, and on 

 the full growth of palpi and false feet the animal attains 

 maturity.* 



* See figure in Intellectual Obseever, 1863, p. 416, fig. 2. 

 VOL. VII. — NO. III. 



