1 9 13-1 4.] Abnormal Echinoids in the Royal Scottish Museum. 243 
“ Les centres vita ax de l’apex sont dans les ocellaires et non dans les 
genitales, et c’est seulement a l’abri et au contact des ocellaires que se 
torment les nouvelles annles ambulacraires ou que naissent les anules inter- 
radiales.” Again Jackson, in his monumental and masterly monograph,* 
says : “ The ocular plates seem to exert a controlling influence in the building 
up of the corona, as below and in immediate contact with the oculars 
originate the coronal plates both ambulacral and inter-ambulacral ” (p. 35). 
And again : “ If this is true, then the loss of an ocular would cause a failure 
to develop of the plates that normally went with it ; also an abnormal 
position of an ocular should cause an abnormal distribution of the associ- 
ated coronal plates ” (p. 36). 
The present abnormal specimens offer two comments on these statements. 
In the hexamerous Echinus esculentus, the ocular of the posterior 
ambulacrum (say VI.) is wholly subtended by genital 5, which extends 
some distance on both sides of it (Plate, fig. 2, and text-fig. 3). Yet 
this derangement of the ocular as regards its relations with the genital 
plates has not affected the growth of the coronal plates, which spring in 
normal manner from the sides of the ocular. On the other hand, in each 
of the deficient Echinus esculentus and Amblypneustes one ocular plate is 
awanting, and nevertheless coronal plates have still continued to be formed 
all along the exposed margins of the genitals (text-figs. 1 and 2). These 
plates are very irregular in shape and do not belong to the normal coronal 
series, but are sufficient to show that the growth areas are not associated 
in any essential way with the ocular plates. 
IV. Preservation of Specimens. — It may be worth drawing attention to 
the fact that the specimens, though dried, had not been “ cleaned.” In two 
cases, therefore, the sex was able to be distinguished from the shrivelled 
reproductive organs, and in one case examination of the cruder internal 
structures was made. 
II. Examples of Incomplete Development. 
(i) Amblypneustes ovum (Lamarck). 
The specimen is a male example of Amblypneustes ovum collected at 
the National Park, Wilson’s Promontory, Victoria, N.S.W., in October 1910, 
and presented to the Museum among a number of others by Lord Carmichael 
of Skirling. 
The test, when examined, was dry and denuded of spines. Its maximum 
* Jackson, R. T., “The Phytogeny of the Echini, with a Revision of the Palaeozoic 
Species,” Mem. Boston Soc. Nat. Hist., vol. vii., 1912. 
