72 Transactions of the [7our>.^i.Feb"n'm 



III. — 0)1 an Uiideserihcd Stage of Development of Tetrarhynclius 



CoroUatus. 

 By Alfred Sanders, M.K.C.S., F.E.M.S. 



(Read hfore the EoYAL Microscopical Society, January VI, 1H70.) 

 Plate XL. 



Being engaged in the course of the autumn before last in researches 

 which necessitated the dissection of a great number of the common 

 Hermit Crab (Pagurus Bernliardus), I found in the tubules of the 

 liver of one specimen numerous cestode worms which appeared to 

 be remarkable ; not having at the time leisure to pay attention to 

 them, they were put aside in a solution of glycerine in water until 

 a favourable opportunity should occur for investigating them more 

 minutely. Before entering on an examination of the relations of 

 this animal, I will give a description of its anatomy. Its total 

 length is about 14'""^'. It is divisible into a head, neck and body ; 

 the head and neck measure rather more than 9"™, the body occu- 

 pying the remainder ; the head is provided with two regularly oval 

 flaps approaching each other obliquely towards the anterior extre- 

 mity, there leaving between them a space slightly convex, in which 

 are situated the openings of four proboscides arranged in a quad- 

 rangular manner ; the neck is long and slender, and tapers shghtly 

 towards the head ; it contains the above-mentioned j)roboscides, 

 which are the distinctive features in the anatomy of this animal. 

 Each proboscis consists of three parts : the anterior contains a 

 protrusile tube, whose parietes are separate and distinct from those 

 of the proboscis itself, but which are continuous anteriorly ; this 

 tube is provided with numerous hooks, arranged in oblique rows ; 

 their bases are inserted into the inner surface of its walls, and their 

 points are directed towards the centre, the whole arranged in such a 

 manner that when the tube is exserted, it is turned inside out, so 

 that the inner surface of the wall becomes the outer, and the points 

 of the hooks are then directed outwards. The hooks vary greatly 

 in size and shape, some being long and narrow, others short and 



EXPLANATION OF PLATE XL. 

 Fic;. 1. — Larva of Tetrarhynchus Corollatutt. 

 „ '2. — One of the proboscides seen as a wliole. 

 „ .3. — Hooks of various sizes and shapes. 

 „ 4. — Smooth fibres embracmg the end of the doutigeroiis tube, the external 



envelope havino; been removed. 

 „ f>. — Smooth fibres entering nniscular part of the tube, showing projection of wall . 

 „ (). — Transverse section of muscular part, showing position of smooth fibres in 



tube. 

 „ 7. — Part of longitudinal section of same, showing direction and arrangement 



of fibres. 

 „ 8. — Separated portions of muscular fibre more liighly magnified : in the 



lower row is the bcvelkd-oflf end of one fibre, otliers are acen breaking 



up into fibrilhc and diaks. 



