CURRENT LITERATURE. 95 



Sepiola, whilst the curious Mediterranean Hctcroteuf.his furnishes a connecting link 

 between them and Rossia. Several characters of Idioscpius and Sq^iadarium, such 

 as the presence of median and lateral adductor muscles to the mantle, the consti- 

 tution of the liver-capsule by an undifferentiated muscle layer, and ics connection 

 with the mantle, the structure of the testes and liver and arrangement of the salivary 

 glands, are also common to the Sepiolidae. Other characters again, such as the 

 structure of the radula, the undivided pallial nerve, and the presence of an accessory 

 median mantle adductor, are most easily understood as modirications of the arrange- 

 ment found in the Sepiolidae. An anatomical character quite peculiar to Idiosepius 

 is the presence of an incomplete right oviduct; the glandular terminal part is as 

 well developed as in the left side, but the internal aperture appears to be absent, so 

 that only the left oviduct is functional; this is probably an inheritance from the 

 oegopsid stem. Hence it appears that the whole anatomy of these forms, except the 

 position of the hectocotylus, indicates a relationship with Sepiola and its allies, 

 rather than with Sepia and Loligo, and the hectocotylisation cannot be regarded as 

 invariably a safe standard of affinity. In conclusion. Dr. Appellof proposes the 

 erection of a new family for Idiosepius, and would arrange the forms in question as 

 follows: — 



Family Idioscpiidac: — Idiosepius. 

 Family Sepioladae. 



Subfamily Scpiadarii: — Sepioloielca, Sepiaclarium. 



Subfamily Scpiolini: — Sepiola, Inioteuthis, Stolotcidhis. 



Subfamily HetcroteiUhinae: — Reteroteuthis, Nectoteidliis. — W. E. H. 



Heath, H. — The Development o( Ischnoehiton. Zool. Jahrb. (Abth. f. Morph. ), 

 1899, Bd. xii, pp. 567—656, T. 31—35, and 5 figs. 



Professor Heath is to be congratulated on the completion of this beautifully 

 illustrated and really excellent piece of work. 



Jschnochiton ( Stenoradsia) magdalcnsis, Hinds, which forms the subject of this 

 research, occurs in great numbers on the Californian coast. During the day it is 

 found either half buried in the sand or concealed under loose stones. It is exceed- 

 ingly sensitive to light and comes out only at night to feed on the vegetation. The 

 eggs are laid in May and June, and unlike any Chiton yet described, it deposits 

 these in the form of "jelly masses," which are strings 3 — 4 mm. in diameter and 

 about 77 cm. long. As the eggs pass out from the ovary they are surrounded by 

 albumen and become moulded into strings by the lower end of the oviduct. On one 

 side of the string there is a strip of albumen in which the eggs are absent, it is 

 therefore not in a state of tension like the remaining portion which is full of ova, 

 consequently the strings assume a spiral form. A specimen kept in the laboratory 

 showed that about 7 inches of the egg-string was laid per hour. Although a very 

 large number of eggs are deposited — the author estimates the minimum for each 

 individual at. 101,804, ths average 115,940, and the maximum 193,564 — very few 

 develope into adults. 



Development proceeds rapidly. The embryo escapes from the egg about the 

 seventh day, and in another ten or twelve days takes on the external characters of 

 the adult. Particular attention has been paid " to the cell lineage, and the external 

 features of the development through the formation of the trochophore and its 

 metamorphosis, up to the assumption of the adult form." The development of the 

 various internal organs is only incidentally referred to in connection with its bearing 

 upon the complete understanding of the external structures, but we are promised a 

 further study of these at a later date. 



Not the least interesting part of Professor Heath's work is the chapter devoted 

 to " General Considerations." Of recent years there has been a growing tendency 

 to regard "the early cleavage stages as something more than a mere manifestation 

 of simple mechanical forces." In the origin and position of the various quartettes 



