Spermiogenesis of the eupyrene sperm in the snail, Fusitriton oregonensis, was studied with light and electron microscopes. Endoplasmic reticulum, which encircles the nucleus in each spermatid, appears to connect with the Golgi body and to interconnect between adjacent spermatids via cytoplasmic bridges. It is suggested that as the Golgi body migrates around the nucleus the endoplasmic reticulum may circulate with it. The alignment of the proacrosome with the nucleus is effected by a 180° rotation of the Golgi body, after which it separates and migrates posteriorly with the residual cytoplasm. Each sperm possesses a well‐developed intracellular digestive system as indicated by multivesicular bodies, residual bodies, and myeloid figures. Autophagy begins in the residual cytoplasm before it is released from the middle piece. Microtubules are found outside the nucleus and mitochondria during the final stages of spermiogenesis, when elongation is almost complete. These microtubules appear to be involved in the final shaping and twisting process, in which torsion is locked in the nucleus and the mitochondria spiral around the axoneme. The annulus attaches the distal centriole to the plasma membrane in the early spermatid and as flagellar production begins they move towards the implantation fossa at the base of the nucleus. There are two centrioles in the early spermatid, the distal centriole and procentriole. The small procentriole fuses with the distal centriole in the intranuclear canal to form the centriolar cap of the basal body. This cap is pushed through the end of the nuclear tube and is separated from the subacrosomal space by only the nuclear membranes.

Decalcification of echinoderm tissues for electron microscopy can be achieved after glutaraldehyde-osmium fixation by treatment with a 1:1 mixture of 2% ascorbic acid and 0.3 M NaCl for 12-24 hours. Electron photomicrographs of material decalcified by this procedure are superior to those from EDTA-treated tissue and show few of the deleteriour effects produced by EDTA.

The feeding mechanisms of Ophiocomina nigra have been re-examined. A new mechanism, the mucus-net method, is described for the first time. This is essentially a method of suspension feeding in which seston is trapped in a net of mucous threads between the arm spines. The entangled material is formed into boluses by simultaneous activities of ciliary currents and the tube-feet and is transported to the mouth by the tube-feet.

The general histology of the integument of the ophiuroid Ophiocomina nigra is outlined. Two types of integumentary mucous glands are described in detail for the first time. The first is a multicellular gland, the basal end of which is located deep within the calcareous layer of the integument. The source of the secretion is a variable number of nuclei embedded in a common cytoplasmic mass filled with fine basiphil granules. These cells contributed their secretion to a duct which pursues a tortuous course through the integument. The ducts frequently branch and anastomose so that any one exit pore may extrude mucin derived from a number of separate, polynuclear sources. The structure so formed is, thus, a massive, multicellular gland. Histochemical studies demonstrate that the mucin is a highly sulphated acid mucopolysaccharide. The second type of mucus-secreting unit is a unicellular gland usually located superficially in the calcareous layer or sometimes restricted to the epidermis and distributed universally over the body. The secretion product of these cells is shown histochemically to be a simple acid mucopolysaccharide. The mucin secreted by the tube-foot glands is demonstrated also to be a highly sulphated acid mucopolysaccharide.The function of these secretions has been investigated to some extent. The massive glands secrete only under conditions of alarm and it is suggested that this mucus serves as a defence against predation. The unicellular glands secrete in a periodic fashion correlated with the act of feeding. This secretion is probably utilized in a suspension-feeding mechanism.

In a holothurian and an ophiuroid, tritiated glucose and glycine in great dilution are removed from seawater by uptake through the skin. Cells differ in their competence to metabolize specific nutrients, an indication that there are specialized cellular responses to exogenous organic molecules. Embryonic ophiuroid tissues have an exceptional capacity for assimilation.