144 E. W. MACBRIDE. 



Like every student of Echinoderms^ I cherish a great 

 respect for the judgment of Ludwig ; at the same time I must 

 express regret at what seems to me to be the roughness of his 

 methods. His figures are most diagrammatic ; his distinction 

 of the ampulla from the axial sinus is, by his own confession, 

 mainly founded on one lucky section ; and his figures of the 

 blood-vessels are such as to render it impossible to conclude 

 anything as to the histological nature of what he saw. Of 

 course, at the time when the work was done the modern tech- 

 nique was undeveloped. 



The work of Christo-Apostolides (1) was conducted with 

 such crude methods, and contains results so contradictory of 

 every one else, that its discussion would, I think, be mere waste 

 of space. Hamann (7) has given a valuable paper on the 

 Ophiuridese; he follows Ludwig^s interpretations, but gives 

 far better figures. But he himself thinks it necessary to 

 apologise for the imperfect preservation of many of his speci- 

 mens. His results are chiefly founded on Ophioglypha 

 albida; in venturing to criticise them I do so with some 

 reserve, as I have only studied Amphiura squamata, but I 

 cannot help thinking that my results throw some light on the 

 appearances described by Hamann and others. Hamann 

 figures the ovoid gland enclosed in a great sinus, which com- 

 municates with the perihsemal ring canal. I suspect that he 

 has confused shrinkage spaces with part of the axial sinus. 

 The ovoid gland he found to be lacunar when he used ^ per 

 cent, osmic acid. I have already pointed out the great care 

 which must be taken to ensure the due penetration of this 

 fluid ; when I used weak osmic, and left the animals only a 

 short time in it, I got the ovoid gland very " maschig,'' the 

 plasma being, in fact, macerated out from the supporting 

 fibres. As to the blood-vessels, I call attention especially to 

 the following passages : — " Die Waudung ist eine diinne Mem- 

 bran ;" " Dieser Membran liegen aussen ovale Zellkerner auf ;^' 

 " Irgend welche Zellsubstanz ist nicht Vorhauden " " Die 

 Blutfliissigkeit stellt eine geronne Masse dar welche sich mit 

 neutraler Karminlosung helbrosa farbt." Now it seems pos- 



