626 EDWARD POTTS. 



leave to reproduce for comparison figs. 3 and 4, and 9, 

 10 and 11, PI. 35, given by Alfred Gibbs Bourne and F. A. 

 Parsons in their descriptions of a certain hydroid found in 

 the Regent's Park Gardens (but in other tanks than those in 

 which the Limnocodium had been discovered), and assumed 

 to be the hydroid condition of that medusa. I have not been 

 informed that such a derivation had been actually traced .^ 



The remaining figures of Plate 36 (one or two exceptions 

 noted) have been very accurately copied by F. von Iterson, 

 artist, from excellent drawings made some years ago by my 

 friend. Dr. John A. Ryder, of the University of Pennsylvania, 

 who was enthusiastic in the study of the polyp with which 

 his name is associated, but who died before the medusa had 

 been seen, much to ray sorrow and to the loss of science. 

 They are — 



Fig. 17 (PI. 36). — A bifid or bi-capitate representation of 

 M. ryderi from life, of which one branch (a) taken by 

 itself may be considered as showing the appearance of the 

 single form of the hydroid, and (fe) as the compound form, 

 where two are found branching near the base : cpm., the 

 capitulum, more or less spherical, terminating the distal end 

 of each mature polyp, and charged upon the surface with 

 varying numbers of n. — neraatocytes or thread-cells ; ]j.d. 

 is the pedal disc or foot, and I. a fully-formed asexual larva 

 about to be liberated from one of the polyps, x 64. 



Fig. 18. — Another bifid form which Dr. Ryder describes as 

 *'a freehand sketch of M. ryderi on the side of the culture- 

 jar with the capitulum of one (much elongated branch ring- 

 like mouth depressed, stem of glass-like transparence, with 

 the exception of cell-ends and boundaries shimmering in the 

 centre." Incomplete '^ basal branch {b) very granular and 

 relatively very opaque." — J. A. R., October 12th, 1891. 



Fig. 19. — Of this Ryder says, " Oral end of adult polyp, 



' This derivation, however, had been traced in 1890 by Fowler. The chief 

 lic!;ure of ilie Limnocodium polyp, showing; a terminal "medusa" in 

 section, is reproduced here in PI. 35, fig. 1. — E. Hay Lankester. 



