Pedicellarice in the Echinidas. Ill 



would seem to be little doubt that the lower chamber is the 

 homologue of the stem-sacculus in Sphcerechinus granulans ; 

 and that such is actually the case would appear to receive 

 demonstration when the immature stages of the pedicellaria 

 glohifera of. S. granulans are taken into consideration. 



In examining a young example of S. granulans it will be 

 found that, in addition to a goodly number of large and appa- 

 rently fully grown sacculiferous pedicellariaz glohiferce, there is 

 also a considerable proportion of the same pedicellarias that 

 . are immature. It will be noted in these that the distance of 

 the stem-sacculi from the valvate head is in relation to the 

 size or stage of growth that the pedicellaria has attained ; and 

 also that, in the small examples, the size of the stem-sacculi 

 is proportionally very much larger than in the fully grown 

 organ, the dilatation on the stem not unfrequently exceeding 

 the diameter of the head of the pedicellaria. Still earlier 

 stages may be found in which the stem-sacculi are situated 

 immediately beneath and touching the head (PL XIII. fig. 7), 

 the dense white contents of the swollen sacculi being percep- 

 tible through the transparent investing membrane, and the 

 outer surface being mottled with fine scarlet specks, whilst 

 the contour of the stem-clilatation is globular and often ex- 

 ceeds in breadth that of the head (PL XII. fig. 7). 



I have not yet been able to study these early phases of the 

 pedicellaria glohifera as thoroughly as is desirable ; for inhe 

 simple spirit-preparations, which are unfortunately the only 

 ones that I possess of these stages, the delicate and very sen- 

 sitive nature of the mucus-gland has defied that method of 

 preparation, and I am in consequence unable to say any thing 

 at present as to the internal and minute anatomy of this 

 early form of the pedicellaria. The drawing, of which fig. 7 

 is a reproduction, was made from a fresh specimen, immedi- 

 ately after removal from the test. That this stage represents 

 the adult form of the pedicellaria glohifera in E. melo, will 

 be at once suggested by a reference to the figures here given. 



A number of small bodies are also present upon the test 

 which appear to be a still more primitive stage of our pedicel- 

 laria, in which the organ is represented by a minute clubbed 

 stem ; but I am at present unable to say definitely whether 

 these bodies are really the normal primitive stage of the 

 sa.ccvlifevous pedicellarice glohifero3 7 or whether they are simply 

 abnormal shafts upon which only the stem-sacculi have been 

 developed. 



Admitting that the phases of growth of the pedicellaria? 

 correspond with the stages above enumerated, the conclusion 

 is almost unavoidable that the pedicellaria glohifera of Splice- 



