50 Echin. 
XIV. ECHINODERMA. 
Delage (86) Zool. Rec. 1900, & Rawitz (255) with general discussion 
of the question ; Boveri (42).—Reply to Boveri (42); Delage (87): 
Rawitz (256) p. 464.—Parthenogenesis, a natural tendency, most 
marked at critical period of maturation (see r. iv), and set going by 
an excitant which may be of various nature, proved by experiments 
on Aslerias glcicialis and Strongylocentrotus ; Delage (88). —Effects 
of reagents on ovum of Asterias glacialis at critical stage, upsetting 
equilibrium ; Delage (89) p. 872.—Effects of reagents on ova of 
&’trongylocentrotus and Asterias , histologic phenomena, comparison 
with natural parthenogenesis ; Delage (90).—Proportion of mag¬ 
nesium in $ and products of Strongylocentrotus lividus opposed to 
theory of Loeb (152) Zool. Rec. 1899; Delage, Y. & M. (91).—Effect 
of MgCl 2 solution : on ripe and unripe Ech. ova ; PrOwazek (247) 
p. 457, footnote : on unfertilised ova of Toxopneustes variegatus , 
segmentation with half usual number of chromosomes, incomplete 
mitosis, formation of cytasters and centrosomes even in enucleated 
fragments, compared with those of normally fertilised ova ; W ilson 
(322 & 324): ditto, production of plutei, description of internal 
changes ; Wilson (325 & 326).—Artificial parthenogenesis or ‘pseudo- 
gamy’ due, among other causes, to dehydration and variation of 
osmotic pressure, 1 tonogamy ’ and not to be confused with results of 
true fertilisation; Giard (132).—Differences of osmotic pressure 
needed to induce artificial parthenogenesis in Echinoderms and Chaeto- 
pterus ; Loeb (189) p. 449.—Sea-water condensed until isotonic with 
Loeb’s 10%—15% 2 \n sodium chloride solutions causes development 
of unfertilised ova of Arbacia ; Hunter (159).—Experimental parthe¬ 
nogenesis, as of Loeb, Morgan, Hertwig, Giard, perhaps due to 
osmotic pressure; Bataillon (14) pp. 169-171.—General discussion 
of osmotic pressure and influence of various substances, with reference 
to work of Loeb, Herbst, Driesch ; Bataillon (15).—Shaking in¬ 
duces development of ova of Asterias forbesii ; Mathews (204).— 
Artificial and natural parthenogenesis compared, reply to Yiguier 
(343, 344) Zool. Rec. 1900 ; Loeb (189).—Experiments on ova of 
Sphaerechinus gramdaris, Toxopneustes lividus , and Arbacia pustulosa, 
obtain no definite result with Loeb’s solutions, but find partheno- 
genetic segmentation accidentally taking place under [supposed] 
natural conditions, the parthenogenetic larvae of Arbacia being 
structurally different from normal larvae : a general criticism of 
Loeb, Giard, Delage and others; Yiguier (312).—Repetition of 
experiments of (312) to eliminate possibility of intra-ovarial fertilisa¬ 
tion and contamination of water by sperm ; absence of membrane in 
parthenogenetic larvae, as postulated by Loeb, is noted ; Yiguier 
(313).—Methods of sterilisation employed by Loeb not applicable to 
Algerian forms of Toxopneustes and Sphaerechinus, and least of all to 
Arbacia ; Yiguier (314). 
III. DISTRIBUTION. 
A. GEOGRAPHICAL. 
i. General : —Power of migration of adult Asterias ; Mead (207) 
p. 205.—Echinoderm larvae found N. of 50° 1ST. lat.; Mortensen 
(214).—Modern bathymetric distribution of stalked crinoids compared 
with ancient; Seeliger (275) p. 46.—General discussion of bipolarity, 
evidence from Echinoderms adduced by Ludwig & Theel (p. 250), 
similarity of brood-pouches in northern Cucumaria glacialis and 
southern C. laevigata (p. 251), possibility of distrib. of free larvae 
dismissed (p. 255), former uniformity of conditions as suggested by 
