THE EARLY INFLUENCE OF THE SPERMATOZOAN UPON THE 

 CHARACTERS OF ECHINOID LARV/E. 



By David H. Tennent. 



The question of the influence of the spermatozoan upon the character of 

 the larva has been the basis of a vast amount of discussion among students 

 of embryology. From the time of the early disagreement between the animal- 

 culists and the ovists it has proved a fruitful subject for speculation. 



In more recent times, since the evolution of the school of developmental 

 mechanics, various attempts have been made at an exact determination of 

 the r61e played by the spermatozoan or by some of its parts. It is conceded 

 that the characters resident in the male parent are transmitted to the off- 

 spring by the spermatozoan, either by the chromatin or by the cytoplasm, 

 or possibly by both. But there is no general agreement as to the time in 

 the individual history when "paternal" characters may become evident. 

 There is a fairly general opinion that the egg conditions development, that 

 it is responsible for at least the early developmental processes, and that the 

 sperm, although instigating development, places no paternal stamp on the 

 offspring until relatively late. 



Boveri's (1895) classical experiment, criticized adversely by various 

 investigators, but confirmed by Herbst (1907), in which enucleated egg 

 fragments of one species of sea-urchin, fertilized by sperm of another species, 

 gave rise to larvae which were paternal with respect to the skeleton, showed 

 that in the absence of female nuclear material the sperm nuclear material 

 might assume the direction of some phases of development by the time of 

 the pluteus stage, but there has been little evidence, one way or the other, 

 regarding ^^ounger stages. Here the evidence has been negative in so many 

 instances that a positive generalization is often heard to the effect that in 

 development the influence of the spermatozoan is not shown in the character 

 of early embryos. 



The discussion between Boveri and Driesch on this subject, in 1903-04, 

 resolved itself finally into a simple difference of opinion in regard to the 

 earlier or later time at which certain characters made their appearance in 

 Echinoid hybrids. Boveri (1895, 1903, 1904) presented evidence on the 

 form of the larvae, the skeleton, the number of chromatophores, the pigment 

 content of the chromatophores, the arrangement of the chromatophores, 

 the number of primary mesenchyme cells, and, under certain circumstances, 

 9 129 



