50 THE AMERICAN ARBACIA 



d. Hermaphroditism 



Hermaphroditism is quite rare in Arbacia, as also in other sea urchins, 

 but it does occur. Among the many thousands oi Arbacia opened in the 

 course of twenty-five summers at Woods Hole, I have found only two 

 cases of well marked hermaphroditism. One was fully described by 

 me in 1939 a. This animal appeared to have four red ovaries and one 

 whitish testis with oozing sperm. On careful examination it was found 

 that each of these gonads had a very slight amount of tissue of the oppo- 

 site sex. The eggs from this animal were readily self-fertilized and 

 developed normally into normal plutei. One summer (July 10, 1946, 

 unpub.) an animal was opened which was to all appearances a female, 

 but some of the eggs became fertilized without applying sperm, and no 

 male had been opened, so that contamination was unlikely. On a care- 

 ful examination, it was found that there were small bits of testis tissue 

 in two of the ovaries, and sperm from this tissue, after becoming motile 

 in sea water, would fertilize the eggs. It seems likely from this experien- 

 ce, that most cases of supposed contamination resulting in accidental 

 (and provoking) fertilization of eggs, such as many competent investi- 

 gators have occasionally observed, are due not to carelessness in tech- 

 nique but to a very slight hermaphroditism of the animal, the testis 

 tissue being too small to be detected. 



Three other cases of hermaphroditism in Arbacia punctulata have been 

 reported, two by Heilbrunn (1929). In one of these, there were four 

 ovaries and one ovotestis, and in the other, two ovaries, two testes, and 

 one ovotestis. Both of these gave rise to normal larvae when self- 

 fertilized. Shapiro (1935 a) described an animal with four testes and 

 one ovary, but the development of the eggs when self-fertilized was 

 abnormal and only a few developed to gastrulae. K. C. Fisher found 

 a case of hermaphroditism (July 10, 1942 unpub.) among the ^r^a«a 

 used in his physiology class at Woods Hole; this animal had three 

 ovaries with some testis tissue and two testes. These eggs when self- 

 fertilized developed normally into plutei. In 1954, Mrs. Cornman 

 observed an Arbacia spawning spontaneously when the collector brought 

 in the animals. Eggs came from four gonopores, sperm from one. The 

 spawning could be controlled at will with the electric current applied 

 to the shell (see under c. Sex Determination). 



References to hermaphroditism in other species of sea urchins and 

 above data for Arbacia punctulata are given below. 



