March 1, 1898.] 



KNOWLEDGE 



67 



Wb regret to record the death of Prof. T. Jeffrey Parker, 

 F.R.S., whose decease occurred on the 7th November last. 

 He was the eldest son of the well-known osteologist, 

 William Kitchen Parker, and was born in London in the 

 year 1850. Obtaining the associateship of the Royal 

 School of Mines in 1871, he, after a short appointment as 

 science master in Yorkshire, returned to London and 

 became demonstrator under Prof. Huxley, at the latter's 

 invitation, at the Royal School of Mines. In 1880 he left 

 England for New Zealand, to take up the duties of 

 Professor of Biology in the University of Otago, which 

 post he retained till his death. Prof. Parker was the 

 author of a great number of original scientific memoirs, 

 some of which are of far-reaching importance. He also 

 wrote some valuable text-books on natural science, one 

 of which, to wit, "Lessons in Elementary Biology," has 

 been translated into German. In conjunction with Prof. 

 Haswell, of Sydney University, he attempted the laborious 

 task of writing a large text-book of zoology, which he was 

 not destined to see in circulation. Prof. Parker was 

 entrusted with the task of forming a museum of biology at 

 the Royal School of Mines, on the type system. He 

 advocated the study of the lower organisms first in pre- 

 ference to the vertebrates, as inculcated by Huxley, and in 

 due course secured a triumph over his great teacher on 

 this point. As a worker, Prof. Parker was of the first 

 rank, and also a luminous teacher. He was a kind, 

 considerate, and lovable man, and the biological world is 

 the poorer by his untimely death. 



THE KARKINOKOSM, OR WORLD OF 

 CRUSTACEA.-II. 



By the Rev. Thomas R. R. Stebbing, ji.a., f.r.s., f.l.s. 



IN the previous chapter examples were given to show 

 the extreme divergence of form and structure to be 

 found in the Crustacea at large. The difl'erences 

 are scarcely less striking that may be seen within 

 the limits of the Malacostraca. Yet that group, by 

 the close interweaving of affinities, is as inseparably com- 

 pacted together as any in the animal kingdom. Especially 

 notable is one character which may be traced through all 

 its divisions. The somites, or segments of the body, are 

 in a numerical bondage ; they are never allowed to exceed 

 twenty-one. That might not seem wonderful were it not 

 that, in the segmented appendages of these same animals, 

 there is frequently shown the most contemptuous in- 

 difference to arithmetical restraints. 



As to the mystic number twenty-one, though it is never 

 transgressed, the chance spectator will never find it fully 

 developed for straightforward counting and ocular demon- 

 stration. It is only discoverable by inferences and 

 comparisons. Always some of the segments are in more 

 or less complete coalescence. This fusion might lead to 

 confusion, did not the following rule provide a guiding 

 light. Wherever a segment can be definitely proved to be 

 single, it never bears more than a single pair of appendages ; 

 elsewhere, then, the presence of two or more pairs of 

 appendages in apparent attachment to a single segment 

 may safely be taken to imply that such a segment is in 

 reality composite. Moreover, composite segments which 

 have lost their appendages present no great difficulty, 

 because they can be compared with corresponding segments 

 which in other genera and species have retained their 

 Often, in a male crab, the pleon or tail- 



part has such an unfurnished compounded segment, which 

 plamly tallies with separate appendage-bearing segments 

 in the other sex. When, therefore, we read of a genus in 



A. Jlemimerus lalpoides%. 

 B. Hem 



D. Dipeltis carri (from Srliuchert). 

 ■nerus talpoides ? . 



which the male pleon has five segments and the female 

 seven, it does not mean that nature has been more stingy 

 to one sex than to the other, but only that in the mascuUne 

 tail three segments have been soldered into one. With 

 regard to the last segment, or telsou, there is this 

 difficulty : it never has distinct appendages. Consequently 

 its character has been aspersed, as though it were not a 

 segment at all, but only a caudal excrescence— Uke the 

 child which fancied itself a first-class carriage, whUe its 

 playmates regarded it as nothing but a truck. The first 

 segment, like the last, has had its , 



claim disputed. It is rarely free 

 and independent. It carries the 

 eyes, which some naturalists do not 

 consider to be true appendages. 

 Often, indeed, the eyes are "sessile" 

 — that is, seated under the skin of 

 the head, with nothing limb-like 

 about them. On the other hand, 

 the "ocular segment" is some- 

 times movably articulated, and 

 often the eyes are placed on jointed 

 stalks, freely movable, and some- 

 times of great length. Between the 

 two debatable points there lie 

 nineteen undisputed segments, 

 verified by nineteen pairs of un- 

 doubted appendages. These begin with two pairs of 

 antennii3 and a pair of mandibles. It is a matter of 

 convenience that throughout the Malacostraca every seg- 

 ment should have its constant number, from the first to 

 the twenty-first. Consequently, although in the sessUe-eyed 

 division the first is always either wanting or undecipherable, 

 that need not interfere with our reckoning the mandibular 

 segment uniformly as the fourth. 



Here it should not be entirely overlooked that, though 

 insects have no stalked eyes and have only one pair of 



c. Dipeliis diplodiscus. 



