Note
Ultrastructure of spermatozoa in artificially induced tetraploid mussels, Mytilus galloprovincialis, was examined by light and electron microscopy and compared to that in normal diploid mussels. Sixteen tetraploid mussels were examined. Eight were found to be males, seven had spent or undeveloped gonads for which sex could not be determined, and one was an hermaphrodite. Ultrastructure of spermatozoa from tetraploids was similar to diploids, but there were some differences.