734 SUMMARY OP CURRENT RESEARCHES RELATING TO 



at the point of least resistance, into the enteric cavity, and so escape by 

 the mouth to the exterior. Although this phenomenon has been observed 

 by Graff in several Proboscida, it has never yet been seen in the family of 

 the Mesostomida. Castrada radiata and Gyrator hermaphroditus were also 

 common, but on the whole the Turbellarian fauna of these lakes appears to 

 be small. 



MoUusca. 



Anatomy and Histology of Salivary Glands of Cephalopoda.* — M. L. 

 Joubin has discovered that the pair of salivary glands which in the Cepha- 

 lopoda octopoda lies against the buccal bulb, is not, as has been thought, 

 absent in the Decapoda, but forms a single unpaired gland which lies 

 beneath the oesophagus, and is closely connected with the muscular bundles. 

 The gland found on one side of the tongue of Octopus vulgaris by M. Livon, 

 has been detected by the author in all the species which he has examined ; 

 the acini of which it is composed open into the space which separates the 

 tongue from the mandible. 



In Octopods, the extra-bulbar salivary glands are situated in large 

 blood-lacunsB, and the blood which supplies them escapes peripherally by 

 a large number of pores which are really spaces between the superficial 

 acini. In Decapods the glands are not bathed in a blood-sinus, and the 

 blood which traverses them is collected by a venous plexus. 



If sections are made of glands taken from living animals, and very 

 carefully prepared with osmic acid, it may be seen that in all Cephalopods, 

 the lingual, the unpaired suboesophageal, and the extra-bulbar glands are 

 formed on the same type. They consist of groups of acini formed of some- 

 what short cylindrical cells filled in their lower third by protoplasm, with 

 a large nucleus ; in the median third there is a plexus of protoplasm, and 

 the rest is filled by rather large granulations which colour deeply. They 

 have a close resemblance to the serous cells of Vertebrates. On the other 

 hand, the pair of abdominal glands is formed by large conical cells, of 

 which the narrow lower part contains the protoplasm, while the upper two- 

 thirds are filled with large spheres of mucus ; they have a remarkable 

 analogy with the mucous cells of higher vertebrates. In the Decapoda 

 the abdominal gland is small and acinous, but in the Octopoda it is very 

 large and tubular. All the tubes of which it is made up are twisted in such 

 a way as to form an inextricable plexus, the spaces in which are filled by 

 connective fibres, or large stellate cells, or which form blood-spaces. 



Development of the Squid.t — M, L. Vialleton finds that when the egg 

 of the squid leaves its follicle and falls into the cavity of the body it is 

 ovoid in form and consists of a chorion, the nutrient yolk which forms 

 nearly the whole of its mass, and the formative yolk which is perfectly 

 distinct, and forms a plate which may be easily separated. At its centre 

 (below the micropyle), the plate is thick and formed of a granular proto- 

 plasm which passes insensibly into the peripheral hyaline portion. The 

 germinal vesicle has already disappeared, and the first directive spindle is 

 to be found near the centre of the area granulosa of the formative yolk. 

 After oviposition, this last is a little displaced ; at its periphery two polar 

 bodies are distinguishable, and in the interior there are two nuclei which 

 may be small and distant from one another, larger and closer, or fused into 

 one. These are the male and female pronuclei ; they differ in size, the 

 smaller being the male. The first cleavage groove has the same direction 

 as that taken by the pronuclei in approaching one another. In the second 



* Comptes Kendus, iv. (1887) pp. 177-9. f Zool. Anzeig., x. (1887) pp. 383-7. 



