1916-17.] Experiments and Observations on Crustacea. 293 
half of both is contained within one and the same sheet of articular 
membrane. Consequently from mere inspection of this one type it is 
impossible to say whether the two were primitively separate and have 
since partially united, or whether they have arisen by splitting of a single 
primitive part. Strong muscles are attached to the gutter in the proximal 
half of the lateral lobe. These arise medially from some part of the medial 
endophragmal skeleton. There is little independent movement of the one 
lobe relatively to the other. 
The structure of the two terminal parts of the first maxilla make it 
plain that their function is different, that of the lateral lobe with its stout, 
darkly pigmented prongs being mechanical, that of the medial lobe with 
its long, delicate terminal filaments set with innumerable fine hairs being 
sensory (possibly for special sense, e.g. taste). 
To the existing descriptions of the second maxillae and maxillipeds of 
Glyptonotus I have nothing to add. 
The Alimentary Canal. 
Considered simply as a motor mechanism for intake, onward propulsion 
and expulsion of food, the alimentary canal of many Crustacea, like that 
of vertebrates, is more complicated at either end than in the intervening 
parts, the complexity of the anterior end, as also in vertebrates, being 
greater than that of the posterior. In Glyptonotus the alimentary tube 
consists of a small and elaborately designed foregut (associated with which 
are the oral appendages and the ventral endophragmal skeleton of the 
cephalon), of a large dilated midgut, and of a hindgut of internal volume 
less than half that of the midgut. The separation between the three 
parts is very distinct. The whole tube, with the exception of one part, to 
be mentioned below, runs in a straight line from mouth to anus — see 
fig. 21. 
The Foregut. 
The foregut is practically confined to the cephalon, and may be said to 
terminate at or just beyond the cephalo-thoracic foramen. It begins as a 
short and narrow tube, the pharynx, which runs from the mouth dorsal- 
wards to expand very soon into a dilated chamber, the foregut proper or 
vestibule , to which the terms “ stomach ” and “ gizzard ” have also been 
applied. The use of the term “ gizzard ” (chosen apparently as an improve- 
ment on the older and admittedly unsuitable term “stomach”) is itself 
misleading, for the name suggests that the function of the organ is to 
triturate the food. This idea is disposed of by the condition of the ingesta 
