GENERAL MORPHOLOGY OP THE GROUP. 
Ech. 4 
tions are comparable to the constant and intimate connection that there 
is in all Echinoids between the madreporite and the genital plates. 
Carpenter (9) raises considerable objections to this and other sugges- 
tions by Ludwig. 
Viguier (Arch. Z. exper. viii. “notes, p. 1 ”) replies to Ludwig’s criti- 
cisms [Zool. Rec. xvi. Ech. p. 3], and asserts that the first ambulacral 
piece is really double. 
The more important results of Ludwig’s essay (23) on the Ophiuroidea 
were noted last year [Zool. Rec. xvi. Ech. p. 3]. The full paper contains 
an historical and critical account of the work of earlier observers, and an 
enlargement of some points on which the author has previously insisted. 
The Ophiurids are stated to be provided, like the Crinoids, with a genital 
cord placed within blood-vessels, and on this cord the separate genital 
tubules are set. PI. xvi. fig. 18 gives a useful diagram of the typical 
relations of the organs in an Ophiuran. 
Lyman (27) describes, as existing in Ophiotholia and Ophiohelus 
(gg. nn., see infra) ^ minute spines arranged in bunches and enclosed in a 
thick skin-bag, in form “ resembling long-stornmod agarics, or parasols 
with small shades,” and arranged in two, or even three, parallel vertical 
rows. 
Agassiz (Am. J. Sci. 3, xx. pp. 294-303, 375-390, and Ann. N. H. 5, vi. 
pp. 348-372) discusses “Palaeontological and Embryological Develop- 
ment,” as illustrated by the Echinoidea, and comes to the general con- 
clusion that, as the actual number of species in any one group must 
always fall short of the possible number, “ it is out of the question for 
us to attempt the solution of the problem of derivation, or to hope for 
any solution beyond one within the most indefinite limits of correctness.” 
Bell (3) suggests that the suddenness of the changes observed in onto- 
logical and palasontological development may be explained by the suppo- 
sition that between definite points in organization neither larval nor 
adult forms are enabled to maintain the necessary equilibrium, and that 
consequently the intermediate forms have been so rapidly passed over as 
to make the chance o£ their being preserved practically nil. Inclining, 
however, to the view that our limited opportunities, as well as the im- 
perfect record of the past and the possible falsification of the record in 
species best adapted for investigation, should make us hesitate to favour 
the view that sudden transitions have really occurred, he points out that, 
if they have, there is both embryological and palaeontological evidence at 
present in its favour, and that consequently the two factors in evolution 
here, as elsewhere, seem to run parallel. 
Stewart (34) describes a specimen of Amhlypneustes griseus, in which 
there was an increase, and Bell (6) one of A. formosus, in which there 
was a decrease, in the normal number of ambulacra. 
Sladen (33) describes enormous pedicellariae glcbiferae in Sphoirechmus 
granularis. 
Studer (36) gives an account of sexual dimorphism in Echinodermata, 
and distinguishes those cases in which these are secondary sexual differ- 
ences due to the parent’s care for the young, from others in which 
differences could only be found to be associated with a difference in sex^ 
