ECHINODERMATA. 
633 
connected with one another, whereas, on the other hand, the 
attachment of the parasite to its 'host, however intimate, is 
merely mechanical. The precise mode of attachment is described 
with suitable minuteness. One end of the tube is buttoned on 
to the intestinal vessel, opposite the mesentery ; the other end is 
free, or, in a few cases, firmly interlocked with the head of the 
Synapta. Free molluscigerous sacs, neither end being adherent, 
are also rare. Such exceptional instances do not, as Muller and 
others have supposed, tend to explain the mode of entry of the 
parasite or its previous history. On both these points exact 
knowledge has yet to be sought. After stating the several issues 
involved, Baur concludes by indicating the direction in which we 
are to look for the determination of the most probable. His 
negative results have, at least, this merit— that they clear the 
way for an inquiry in which the difficulties of observation are 
unusuall}^ forttiidable ; and his careful treatment of the whole 
subject displays a skill in analysis which renders the perusal of 
his work especially instructive and Satisfactory. 
Remarks on known species : — 
Grube (pp. 98-100) found about Lossini seven species of Tlolothiridea. All 
of these, excepting Cucumaria tergestina (Sars) had previously been noted in 
his work, ^Actinien, Echinodermeh und Wurmer des Adriatischen und 
Mittelnieers,’ 4to, Konigsberg, 1840. 
Grube gives revised definitions of the following species : Jlotothuria cata^ 
7 tensis (Gr.) ; II. stdlata (d. Chi .) ; II. glahra (Gr.). On each of these he offers 
some comments. II. catanetisis and II. glahi'a are foi* the first time figured. 
Grube has also met with some small Sea-cucumbers, which he supposes may 
be the young of 11. tuhulosa. 
The following species, quoted by Norm AN, are additions to 
the British fauna since the publication of Forbeses monograph of 
the British Echinoderras 
Cucumaria elongata (DUben & Koren) ; Thyone raphanus (D. & K. j ; Psohts 
squamata (D. & K.) ; Ilolothuria nigra (Peach) ; Synapta inhcBrem (Muller). 
Hew species : — 
Psolinus pmillus (Norman), Durham coast; Thyme Jloccosa (N.), Oomish 
coast ; Synapta tenera (N.), Clyde. 
Norman is of opinion that the minute dermal plates of the Rolothuridea 
will afford valuable specific characters. 
Stimpson defines: — 
Pentacta pipet-ata, sp. n. (Stimpson) ; P. populifer (St.) 
ADDENDUM. 
Leydig, F. Vom Ban des thierischen Korpers. Handbuch 
der vergleichenden Anatomie. Erster Band, erste Halfte. 
Tubingen, 1864, 8vo (pp. 278k 
1864. [voL. I.] 3 T 
