REPORT ON THE PYCNOGONIDA. 105 



Different as tie forms of these spines may be, their minute structure is always the 

 same, and, I think, quite identical with that of any other spine. The cuticle is perforated 

 at the place where the spine is inserted, and a thin and flexible part of this cuticle keeps 

 the spine in its place ; a socket is thus formed in which the spine easily moves. The 

 spine itself is, near its insertion, cylindrical and hollow, and its cavity is entirely or 

 partly filled with a protoplasmic substance, which is in continuity with the epithelium 

 of the integument. Towards the extremity the spine is flattened, chitinous, and no 

 longer hollow ; the exterior margin of this flattened part is serrated {Nymphon), or 

 provided with extremely small teeth (Colossendeis). Originally I considered these spines 

 as being of a sensory nature ; but afterwards, as I was convinced of their chitinous composi- 

 tion, I changed my opinion. However, as it is not diflicult to trace a nei-ve, at least in 

 some of the more transparent species, penetrating these spines, they may still be considered 

 a.s, to a certain extent, organs of feeling. On the other hand there are, perhaps, far more 

 important functions to be fulfilled by the ovigerous legs with the aid of these denticulate 

 spines, viz., those of seizing the food, and, last, not least, of holding the animal of the 

 other sex during the act of copulation. In most species where denticulate spines occur 

 the four last joints of the ovigerous legs often lie rolled up spirally, with the row^s of 

 denticulate spines turned inwards. These joints if wound round one of the legs or any 

 other part of the body of the animal with which it copulates, would necessarily secure a 

 very strong adhesion in consequence of the rows of spines. 



In close relation with the integument are the glands, which occur in different 

 appendages of the<ibody. 



1. The glands of the palpi. These I observed in Discoarachne brevipes, where they 

 occur in the third joint of the palpi, and probably theii- secretion is poured out through 

 a sieve-like perforated spot at the end of the second joint (PL VII. fig. 10). In the 

 palpus of Ascorhynchus such a gland is also present. It is situated in the fifth joint, and 

 has the form of a long sack, whose wall is lined by small and very numerous glandular 

 cells. It is attached to the wall of the joint of the palp by means of numerous threads 

 of connective tissue, and it opens towards its distal extremity by means of a rounded 

 pore. In Ascorhynchus orthorhynchus this pore is placed at the tip of a small conical 

 excrescence ; but in Ascorhynchus glaber I did not observe this knob. Probably the 

 same glands occur also in other genera — e.g., in Colossendeis — but I could not ascertain 

 their presence.^ 



2. The glands of the ovigerous legs. These I oliserved in Nymphon, but their minute 

 structure can only be studied in fresh specimens. They open into a small pore, not far 

 from the beginning of the fourth joint of the leg. Each gland seems to consist of the 



' The glands of the palpi are mentioned in Dohni's paper of 1879. He says of the nerve of the palpus : " Er um- 

 fasst auf seinem Laufe ein sonderbares, bisher unbekannt gibliebenes Excretionsorgan " {loc. cit., p. 31). 



(ZOOL. CHALL. EXP. PART X. 1881) K 11 



