478 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
cliirotous trunk which early gave off a Synaptid, and later a Molpadiid 
branch. As to the Elasipoda, he does not believe that they form a group 
equal to the Dendrockirotae and Aspidochirotas, but that they are an 
offshoot from the latter. 
The primitive Holothurian would have ten simple cylindrical ten- 
tacles provided with feeble tentacular ampullae, which sprang from the 
five radial water-vessels, as did also the pedicels, which were limited to 
the rays and provided with ampullae ; it would also have a calcareous 
ring formed of five radials and five interradial pieces ; the transverse 
musculature of their body-wall formed an unbroken circular layer, the 
simple longitudinal muscles gave off no retractors ; the stone-canal was 
simple, fixed in the dorsal mesentery, and directly connected with the 
exterior ; the genital tubes were symmetrically developed on either side 
of the dorsal mesentery ; auditory vesicles lay on the radial nerves ; 
the respiratory tree and a simply arranged enteric blood-vascular system 
were developed, and the enteron took the course characteristic of Holo- 
tkurians, while the integument was filled with fenestrated calcareous 
plates formed of hexagonal meshes. 
Prof. Ludwig gives the following phylogenetic diagram : — 
Synap- 
tidae 
Elas ip o da 
Molpa- Dendro- Aspido- Psychro- Deima.- Elpi- 
diidae chirotse chirotae potidae tidae diidae 
A criticism is made of the work of preceding systematists, some of 
whom fell into misleading errors. In all but the Synaptidas all the feet 
and tentacles arise from the radial vessels which mark the rays of the 
plan of structure of the body, and they may, therefore, be called Actino- 
poda ; in the Synaptidae, however, some of the tentacular feet enter into 
relation with the circular canal, and they may, therefore, be called 
Paractinopoda. The following new classification of Holothurians is 
proposed : — 
Class Holothurioidea. 
1st Order, Actinopoda .. 
2nd „ Paractinopoda. 
1st Fam., Aspidochirotae. 
I 1st Subfam.. Psychropotidae. 
2nd „ 
, Elasipoda < 2nd ,, 
, Deimatidae. 
! 3rd ,; 
, Elpidiidae. 
3rd ,, 
, Dendrochirotae. 
4th , 
, Molpadiidae. 
5th ,. 
, Synaptidae. 
