274 THE AMERICAN NATURALIST. (No XXXII. 
Another curious adaptation has been described by Ludwig? 
Chirodota contorta Ludw., also from the Antarctic. In this animal 
the reproductive tubules themselves serve as receptacles for the 
young until they have attained a length of 3 mm. or more, when 
birth takes place through the outer opening of the genital duct. 
Furthermore, the attachment of the eggs of Cucumaria crocea Less. 
and of Psolus ephippifer W. Thoms. to the dorsal surface of the mother, 
where the young are reared, is a fact that is familiar to all naturalists. 
In still other holothurians the eggs have been known to find their 
way in some hitherto unexplained manner into the body cavity, 
where they develop. One of these forms is Synapta vivipara, origi- 
nally described by Oerstedt from specimens taken in the West 
Indies. It is probably identical with Theél’s Synapta picta, which 
the Challenger Expedition took at the Bermudas. 
Synapta vivipara has recently been thoroughly studied by Dr. 
Hubert Lyman Clark? in the Johns Hopkins Marine Laboratory at 
Port Henderson, Jamaica. It is to be found in the quiet pools in 
the rear of Port Royal, clinging to the red seaweed Acanthophora, 
which is attached to the roots of the mangroves. , 
The eggs probably burst through the thin walls of the bisexual 
reproductive tubules into the body cavity ; they were never observed 
in the genital duct, nor were passages from it into the body cavity 
discovered. The duct runs forward into the body wall, but ends 
blindly in the connective tissue beneath the external epithelium. 
Spermatozoa were found abundantly both in the duct and in the 
connective tissue about its blind end ; hence it is believed that they 
pass outward through the epithelium of the end of the duct, the 
connective tissue layer, and the thin external epithelium of the body 
wall. Thence they are believed to make their way to another indi- 
vidual, and by passing inward through the anus and certain apertures 
in the walls of the rectum into the body cavity they meet the ova. 
Apparently ripe spermatozoa and ova occur simultaneously in the 
same reproductive tubule, but there is nothing to indicate that the sper- 
matozoa ever pass from its lumen through its wall into the body cavity. 
Indeed, no direct evidence has been obtained to show either that self- 
_ fertilization does or that it does not take place in Synapta vivipara. 
1 H. Ludwig, Ein neuer Fall von Brutpflege bei Holothurien. Zool. Anz., 
897. 
L. Clark, Synapta vivipara: A Contribution to the Morphology of 
3. 1898. 
H. L. Clark, The Viviparous Synapta of the West Indies. Zool. Anz., Jahrg. 
xix, Nr. 512, pp. 398-400. 1896. 
