METAMORPHOSIS II7 



brought in from the sea. This measured 6 mm. including spines. The 

 spines are more numerous and more slender than in the metamor- 

 phosed animal, but the structure of these spines and the primitive 

 spines is the same. They are transparent, with veins running through 

 them, something like an insect's wing. The stages between the animal 

 metamorphosed in the laboratory and the youngest animal found out- 

 side are much desired. Plutei have not been found in the tow above 

 the beds. 



The account given above has been revised from an earlier account 

 (E. B. Harvey, 1949), which did not include the later stages with well 

 formed primitive spines. Earlier studies on the Arbacia metamorphosis, 

 as well as that of other forms have been treated in Part I (Chapter 2, 

 Section f) under Historical. The best early study of Arbacia punctulata is 

 that of Brooks (1882) and his students, Garman and Colton (1883), 

 published by Brooks in his Handbook of Invertebrate ^oology (1883), in 

 which excellent drawings of the different stages are given. The works 

 of Agassiz (1872- 1 874, 1883, 1904) and of Miss Gordon (1929) should 

 also be consulted. 



b. Other Species 



Many studies on the metamorphosis of other species of sea urchins 

 have been made. Among the most complete studies are those on Echinus 

 esculentus by MacBride (1903, 1914a Text-book of Embryology vol. i, 

 p. 504) and by Shearer, De Morgan, and Fuchs (1914); the develop- 

 ment of Psammechinus miliaris and Ps. microtuberculatus is similar (Mac- 

 Bride, 1914a); Arbacia lixula and Paracentrotus lividus by von Ubisch 

 (1913a, b, c, 1927, 1932, 1950); see also Busch (1849); ^^id Miiller 

 (1854) ; Echinocyamus pusillus by Theel (1892) ; Echinocardium cordatum by 

 M.2iC^r\dt{i^i^h)\Salmacisbicolorhy Aiyar (1935); Mespilia globulus^ 

 Strongylocentrotus pulcherrimus, and other Japanese forms by Onoda 

 (193 1, 1936). A very good list of studies on larval forms is given by 

 Mortensen (192 1, p. 12), and a more recent list arranged phylogeneti- 

 cally by Fell (1948). Studies made during expeditions to Kei Islands 

 (Amboina), Java, S. Africa (Onrust, Mauritius) and Egypt were 

 published by Mortensen (1931, I and II; 1937, III; 1938 IV); and 

 there are many references in his Monograph ( 1928-195 1). See also this 

 Monograph under Historical, Part I, Chapter 2, Section f (p. 18). 



A very good general treatise on larval development may be found 

 in Grasse's Traite de ^oologie, t. 11, p. 307-312, 1948. 



