SUB-FAM. 3. BOLTENINAE.—More than eight folds in branchial sac; tentacles compound; body pedunculated (Fig. 38, A). The chief genera are—_Boltenia_, Savigny, with the branchial aperture four-lobed, and the stigmata normal; and _Culeolus_, Herdman (Fig. 38), with branchial aperture having less than four lobes, and the stigmata absent or modified (Fig. 38, B), the branchial sac showing a wide mesh-work of vessels stiffened by branched calcareous spicules. _Culeolus_ is a deep-sea genus discovered by the {76}"Challenger" expedition; eight or nine species are now known from various parts of the world, ranging in depth from 630 to 2425 fathoms. Most of the species are from the Pacific; only one from the North Atlantic. The curiously curved type of spicule found in the branchial sac and other organs is shown at Fig. 50, C (p. 87). Amongst the Cynthiidae are found most varied conditions of the reproductive organs. The gonads are sometimes on both, sometimes on only one side of the body, sometimes in one or several branched masses, and sometimes distributed as a large number of minute "polycarps" over the inner surface of the mantle. [Illustration: FIG. 39.—Various Cynthiidae. A, two forms of _Styelopsis grossularia_, Van Ben.; B, _Forbesella tessellata_, Forb.; C, _Polycarpa aurata_, Q. and G.; D, _Styela clava_, Herdman; E, _Polycarpa tinctor_, Q. and G.; F, _Cynthia formosa_, Herdman; G, _Polycarpa comata_, Alder; H, _Polycarpa pedata_, Herdman; I, _Pelonaia corrugata_, Forb. and Goods. (After Herdman.)] The family Cynthiidae is the largest section of the Simple Ascidians. The species range from the size of a pea to that of a large cocoa-nut. They are for the most part opaque, and often richly coloured—reds, yellows and rich browns predominating—and so look very different to the grey gelatinous Ascidiidae, and to the sand-encrusted Molgulidae. They extend from between tide-marks (_Styelopsis grossularia_), down to the abysses (_Styela bythia_ and _S. squamosa_ at 2600 fathoms). Some genera (_Styela_ and the closely related _Dendrodoa_), extend far into Arctic seas, but many allied forms (_Styela_ and _Polycarpa_) are also found in the tropics. {77}[Illustration: FIG. 40.—Three simple Ascidians with vascular adhering processes from the test (nat. size). A, _Ascidiella aspersa_, O. F. Müller; B, _Ciona intestinalis_, Linn.; C, _Molgula oculata_, Forb.] [Illustration: FIG. 41.—Branchial sacs of Molgulidae showing curved stigmata. A, _Ascopera gigantea_, Herdman; B, _Molgula pyriformis_, Herdman; C, _Eugyra kerguelenensis_, Herdman.]