S06 Proceedings of the Royal Physical Society. 
The following Communications were then read : — 
I. On the Anatomy of Sacculina with a descriftion of the Species. By 
John Anderson, M.D. Plate XIll. 
Three years ago I drew the attention of this Society to 
the fact of the frequent occurrence of Sacculina and Pelto- 
gaster on some of the Crustacea of the Firth of Forth. For 
some years past the subject of the affinities of these parasites 
has been occupying the minds of many foreign observers ; 
and the following observations, therefore, are brought before 
the Society in the hope that they may tend to throw some 
light upon this difficult question. In the present paper I 
have purposely abstained, as far as possible, from dogmatis- 
ing regarding their systematic position, but elsewhere I have 
referred them to the Cirripedes.* I may mention that the 
relative position of the investing sacs, the character of the 
ovaries and the ovigerous lamellae, and the apparent herma- 
phrodite nature of the adult animal, when viewed in con- 
nection with the larval form, appear to me clearly to indicate 
their Cirripedial nature. Accordingly, in my graduation 
thesis, I created a new order (Sacculinacea) for their re- 
ception, f 
Among recent observers, Leuckart drew the attention of 
naturalists to Thompson s systematic description of Saccu- 
lina, and proposed the adoption of his generic term. " If 
we restore," he says, " the name Sacculina either for Pelto- 
gaster in Eathke's sense, or, at least, for the form character- 
ised by Diesing as Pachyhdella, we are only discharging an 
old, superannuated debt." In the same article he described 
a new form parasitic upon Ryas araneus, and which he 
named Sacculina inflata. In accordance with Leuckart's 
proposal, I use the term Sacculina as referring to the 
parasite alluded to by Cavolini, and as synonymous with 
* Graduation thesis, "Contributions to Zoology." 
t The following are the characters of this order, as given in my thesis : — 
Cirripedia sine segmentis, oculis et appendiculis. Carapax sacciformis et appen- 
diculata est : foramen in carapace situm est. Pedunculus annulo corneo affixus 
est. Os suctorium. Larva prime monocula cum 3 crurum paribus. Cir- 
ripedia parasitica sub abdominc Crustaceorum Decapodorum Brachyurorum. 
