TRANSACTIONS OF SECTION O. 431 



large and in many respects as well developed as the larger Decapoda. However, 

 apart from the few bare statements made by Kowaleveky, the large complex 

 maxillary gland of Squilla has remained undescribed. On opening the thoracic 

 cavity of Squilla, the maxillary glands appear as a pair of large massive organs, 

 with slender ducts running vertically down to the bases of the second maxillae, 

 opening on papilla?, as surmised by Caiman. These maxillary glands, in fact, 

 strongly resemble at first sight a pair of mandibular adductor muscles, and pos- 

 sibly they have been mistaken for such by previous workers. The description of 

 the structure of these glands supplied in the present paper has been derived from 

 a careful examination of two complete series of transverse and one complete series 

 of longitudinal sections through adult specimens of Squilla desmarestii; stages in 

 the early development have also been ascertained from transverse and longi- 

 tudinal series of sections of Erichthus larvae of different sizes. In an Erichthus 

 larva measuring a little over 2 mm. in length the gland merely consists of a 6hort 

 narrow tube opening externally on the maxilla and ending internally in a slight 

 dilatation — the end sac. Excepting those composing the wall of the end sac, all 

 the cells of this young gland show a striated border and were doubtless func- 

 tional. In an Erichthus larva measuring 12 mm. in total length the gland has 

 altered in shape, having become divided into two thin-walled bladder-like com- 

 partments (the kidney proper and the end sac) lying side by side, closely apposed 

 (the two walls only being separated by the narrow haemocoele), and communicat- 

 ing by a small aperture situated at their posterior ends. In a slightly older 

 Erichthus (14 mm.) the walls of all parts of the gland are seen to be undergoing 

 invagination at numerous points, so as to form internal lamellar folds containing 

 extensions of the hasmoccele. In the adult the large cavity of the gland has 

 become almost completely broken up into a network of spaces owing to the 

 further extension and branching of these internal invaginations, and since the 

 two-layered septum dividing the kidney from the end sac has also given off these 

 lamellar extensions on both sides, it is impossible to distinguish clearly between 

 these two regions, the only distinction being that in the end sac the cavity is not 

 so much invaded as in the kidney proper. 



Among other features of the adult internal anatomy may be mentioned the 

 presence of a well-developed Nauplius eye, rectal glands (possibly also rudi- 

 mentary urinary tubules similar to those of Amphipods) and a very short procto- 

 daeum. Orlandi's correction of the old and oft-repeated statement concerning 

 the numerous paired openings of the 'liver' into the gut is valid, but he errs in 

 supposing that the single pair of 'hepatic' ducts (described and figured in the 

 larva by F. M uller in 18G3) are narrow and open dorsally into the pylorus ; on 

 the contrary, the apertures are wide and open laterally. Orlandi's figure (repro- 

 duction of a photograph) is quite misleading. 



2. The Hypostome and Antenna in a reconstructed Trilobite (Calymene). 

 By Malcolm Laurie, B.A., D.Sc, F.L.S. 



In this attempt at reconstructing a Trilobite by Professor Sollas' method, the 

 grinding instrument used was of comparatively simple construction. It consists 

 of a central portion in which is a sliding tube pushed forward by a micrometer 

 screw, just as in a Cathcart microtome. This central block is supported on ivory 

 points placed at the ends of three radial arms six inches in length. Grinding 

 is done on a sheet of plate glass with fine emery and the fossil is brought each 

 time to the exact level of the three ivory points. For photographing, the whole 

 machine is placed in a stand rigidly connected with the camera, and, its position 

 being determined by the three points, it comes automatically into focus. 



Two points of interest have as yet come out of the work, one relating to the 

 position and structure of the mouth, the other to what seems an antennary struc- 

 ture. The mouth has always been considered as opening behind the hypostome. 

 This reconstruction shows the hypostome to be, roughly, pentagonal in shape, 

 with a strong, almost straight, anterior margin. The long oblique posterior 

 margins are comparatively thin and reflexed for the posterior half, as though 

 for the attachment of muscles. The short lateral margins have articular sur- 

 faces half-way down by which the hypostome articulates, with the internal sur- 

 face of the carapace just at the margin of the glabella. Owing to the shortness 



