Spermatozoon of Chimaericola leptogaster.

• A-W, transverse sections, in antero-posterior sequence;
• X, longitudinal section.
• A-C, anteriormost part of spermatozoon; peripheral microtubules and progressive appearance of the two centrioles.
• D, E, one fully formed axoneme and section of the centriole of the other axoneme.
• F-H, peripheral microtubules (full ring in G,H), two axonemes, and mitochondrion.
• I, two axonemes, peripheral row of microtubules reduced to a few units, and mitochondrion.
• J, one axoneme, distal extremity of other axoneme as scattered doublets and central core, a few remaining peripheral microtubules, and mitochondrion.
• K-M, one axoneme and mitochondrion, a few peripheral microtubules.
• N-P, one axoneme, a few peripheral microtubules, mitochondrion and section of the anterior thin part of the nucleus, which is wider as sections are more posterior.
• Q-S, one axoneme, a few peripheral microtubules, mitochondrion, and section of nucleus approximately as wide as axoneme.
• T-W, one axoneme, a few peripheral microtubules, mitochondrion, and wide section of nucleus. W is a very wide section with electron-transparent chromatin. X, typical trepaxonematan axoneme.