DEPARTMENT OF MARINE BIOLOGY. 151 



At Montego Bay specimens with oculars 1, y, also with 1, v, iv insert, are com- 

 mon, but both have passed into the phase of arrested variants and oculars 

 1, v, rv, 11 insert is the local typical feature. This is of interest as showing a 

 progressively differentiated typical character in different localities. The 

 variations in each locality cover practically the same range of characters, but 

 the local character as regards oculars passes from a lower to a higher plane 

 on a perfectly definite line of specialization. For all five oculars to be insert 

 is a progressive variation in the species for all localities. While oculars 1, v, 

 iv, 11 insert exists as a progressive variation in a number of different species 

 of recent echini, the occurrence of this feature as a dominant character in 

 Tripneustes escnlentus at Montego Bay is the only known case of its being a 

 prevailing character in any living species. 



The Spermatogenesis of the Mongoose of Jamaica, by H. E. Jordan, 



University of Virginia. 



An effort was made to secure the maturation stages of Echinaster crassi- 

 spina. The males were ripe in March, but no ripe eggs could be found in the 

 apparently fully developed ovaries. At the time of our visit to Jamaica I 

 was prosecuting a comparative study of mammalian spermatogenesis with 

 special reference to the presence of an accessory chromosome. I was there- 

 fore fortunate in securing in Jamaica excellent material of the mongoose 

 upon which to further extend the investigation. This was favorable for a 

 complete study of spermatogenesis. 



The mongoose, like the cat, squirrel, and pig, shows at no stage any indica- 

 tion of an accessory chromosome. On the contrary, in sheep, mouse, bull, 

 mule, and horse such indication (or of a heterochromosome group) clearly 

 appears at some stage (or stages) of the first spermatocytic prophase, in- 

 cluding synapsis.* 



The inference is strongly suggested that heterochromosomes are simply 

 variously modified ordinary chromosomes, and that if their presence in the 

 male has any connection with sex-determination this connection is not de- 

 pendent upon a specific behavior dependent upon morphology. On the other 

 hand it seems probable, in view of the presence of an accessory chromosome 

 (double) in the egg of the cat, according to Winiwarter and Sainmont, 

 that the element when absent in the male is present in the female. If the 

 presence of an accessory or heterochromosome can be demonstrated, and 

 confirmed by actual counts in oogonial and spermatogonial metaphase plates, 

 in the growing oocytes of squirrel, mongoose, pig, and similar forms, then the 

 close causal connection between sex-determination and heterochromosomes 

 will be more firmly established. 



Material was collected also for a study of the embryology of the mongoose 

 and of the anatomy of its adult brain. 



The Dimorphic Spermatozoa in Marine Prosobranchs, by Edwin E. Reinke, 



Princeton University. 



The main object of this investigation was to determine, if possible, whether 

 the apyrene spermatozoa of Strombiis play any part in the fertilization of the 

 egg. Owing to the lack of ripe eggs of that species, no definite results were 

 obtained. Ripe sea-urchin eggs were then tried, but they had no effect upon 

 either kind of spermatozoa, except in a few instances where the egg-mem- 



* I have already described an accessory chromosome in the opossum and in the bat. 



