434 Prof. Miiller on the Larval State and the Metamorphosis 



Before Pluteus paradoxus exhibits any trace of a star-fish, it 

 has the form figured in PI. XI. fig. 5. It has no further resem- 

 blance to the larvse described by M. Sars than in the appendages 

 being developed in one direction and the animal being bilateral. 

 In other respects the form is so peculiar and so very dissimilar, 

 that it would never be suspected to be the larva of an Echino- 

 derm, notwithstanding the previous observations of M. Sars. 

 The appendages are numerous, viz. eight, and very long ; they 

 have no relation to tubercles and organs for attachment. The 

 elegant skeleton of Pluteus has been already described. We must 

 now add, that it is calcareous and dissolves in acids. The obser- 

 vations made during the present year, for the first time afford 

 an explanation of its further internal structure and vital phse- 

 nomena. The membrane which covers the columns of Pluteus 

 extends over the body of the animal in arches from one column 

 to the other. The intermediate substance descends deeper be- 

 tween two only of the columns which we shall call the posterior. 

 The mouth is situated at the part at which, in my previous trea- 

 tise, I noticed the occurrence of motion. Opposite the mouth 

 at the anterior side, the skin of the body is extended between 

 two of the columns like a marquise over a door. The oblique 

 lower lip projects considerably forward at the mouth. The oral 

 cavity leads upwards into an oesophagus, and this is connected by 

 a contraction with the csecal stomach, which fills the cavity of the 

 body between those columns which are inclined towards each other. 

 The stomach is often divided by a constriction into an ascending 

 portion and a blind pouch recurved anteriorly. Two granular, 

 glandular bodies, of the use of which I am ignorant, are situated 

 on each side of the oesophagus and stomach. Before the meta- 

 morphosis commences, Pluteus paradoxus is rather less than half 

 a line (f ) in size. It occurs in great numbers during the months 

 of August and September in the open sea near the surface, and 

 swims by ciliary motion, usually with the appendages forwards ; 

 but sometimes it continues to revolve horizontally, whilst the azy- 

 gous extremity and the long appendages retain an opposite and ho- 

 rizontal direction. Ciliary motion exists throughout the stomach, 

 in the oesophagus and the cavity of the mouth ; as also definitely 

 distributed on the outside of the body. The mouth is surrounded 

 by a tuft of cilia. The acute, azygous extremity of the animal is 

 also smTOunded by a circular tuft of cilia ; the ciha then expand 

 into the eight long appendages, so that in each there are two 

 rows or tufted lines, upon which they are situated. Both rows 

 or lines at the extremity of the appendage curve into one another ; 

 between two of the appendages or arms the line of cilia runs 

 from one arm to the other on the arches we have mentioned ; 

 thus the entire animal is surrounded by a cihated organ of 



