812 PROF. E. RAY LANKESTER ON THE MUSCULAR AND 
(Quart. Journ. Microsc. Sci., January 1884). Further, I investigated the structure of 
both the simple and the compound (or aggregated) eyes of Zimudus and of Scorpio, and 
again obtained from the minute microscopic structure evidence of the closest agreement 
between these two genera and of total divergence from the Crustacea (Quart. Journ. 
Micr. Sci., January 1883). 
Again, since the structure of the genital ducts in Crustacea is simple or, in any 
case, non-reticulate (except in the male Apus), whilst both oviducts and sperm-ducts in 
Scorpio and other Arachnida have the characteristic form of a mesh-work, I requested 
my pupil Mr. W. B. S. Benham to investigate the structure of the spermatic duct and 
glands of Limulus, hitherto unexplored. Mr. Benham found (and has described in the 
‘Transactions of the Linnean Society,’ 1883) a highly subdivided reticulum, or mesh- 
work, constituting the spermatic duct, as in the Scorpions. ‘The oviduct had previously 
been shown by Owen to have essentially the form of a network. 
Lastly, I have found (and am about to explain in detail in the Quart. Journ. Micr. 
Sci.!) the most intimate agreement between Limulus and Scorpio in respect of the 
following points of minute structure :—(1) the blood-corpuscles ; (2) the softer connective 
tissues ; (3) the entochondrite (internal sternum of Straus Durkheim), which is, in both 
cases, a mass of condensed connective tissue with cells of very characteristic appearance, 
but so like in the two cases as to be practically indistinguishable; (3) the gastric ceca 
and their lining epithelium. 
Amongst the most important points of agreement between Limulus and the Arachnids 
is that insisted upon by Straus Durkheim, namely, the possession of an internal freely 
suspended sternum or plastron of connective tissue (cartilaginoid tissue), to which 
numerous muscles are attached. Such an entochondrite exists in no Crustacean?; it 
probably is more or less closely similar in nature to the so-called “chorda” discovered 
by Leydig in insects of the genus Sphina. 
In order to carry out fully the comparison of the entochondrite of Zimudus with that 
of Scorpio, it became necessary to make an investigation of the muscles attached to this 
organ in each case, and this has led on toa general investigation of the whole muscular 
system and its related supports in the two animals. ‘The investigation of Limulus has 
been carried out by Mr. Benham, that of Scorpio by Miss Beck. No account of the 
muscular system of either animal has before been given, although imperfect descriptions 
of parts of the muscular system of Limulus are to be found both in the memoirs of 
Owen and of Alphonse Milne-Edwards. 
As might be expected, we find a considerable specialization of the muscular system 
in the two animals compared, resulting in a wide divergence as to certain muscles; but 
there remain, nevertheless, certain agreements which are of the most striking and 
important character. 
1 Since published, in January 1884. 
? T haye since found a rudimentary structure of the kind in Apus (Quart. Journ. Micr. Sci., January 1884). 
